First off, thanks to all the folks who answer question on this forum. I have been reading and learning so much from you folks. Thank you!

I am working on a 1987 Ford Cab and Chassis F-350 6.9 litre 4WD with a 5 speed manual transmission. I have been having wicked hard starting issues. I have replaced the forward diesel tank(it was leaking) and all the lines forward, the mechanical lift pump, and the fuel filter. I have placed a see-through line from the lift pump to the filter head with a bulb primer, a see-through line on the fuel filter outlet return line to the #1 injector, and a see through line on the injector pump outlet return line.

I know that the fuel selector valve is working. I have not done the return line o-rings, washer and new line replacement kit yet.

My real question is, it seems as though when I try and prime everything with the bulb primer, that all the fuel seems to go through the return line circuit (as if it is the path of least resistance). When I pinch off the return line from the fuel filter head the bulb will not squeeze at all, like the inlet to the IP is clogged. I replaced the o-rings on the hard line from the filter head to the IP as well.

There is still solid fuel in the IP outlet return line and in all my clear lines after setting overnight, so I do not believe I am losing prime anymore. (I thought that was my original issue).

When I roll the truck down a hill and pop start it in second it runs like a champ. No sputtering, no bad smoking. It seems like the IP is working well and everything is firing as it should. I can shut it off and it starts right back up with no issues. It doesn't die after starting like an air intrusion issue, but if I let it set overnight it takes a ton of cranking to get it going again, even though it appears "primed".

Should I be able to force fuel through the injection pump from by bulb primer with the return line crimped without any issue?

Could the IP inlet screen be plugged, and if so how to I get to it to clean it out?

This is way too long a post as it is. Hopefully someone reads it and can help me out. THANKS in advance.
Ben in Maine.

 

Sounds like you've done everything correctly so far.
I've had the same chronic loss of prime at the fuel filter overnight.
But on my '92 there is a bicycle tire Shraeder valve to bleed air out.
You probably don't have this valve. When mine wouldn't start in the morning, it was always due to air in the fuel filter, which came in through a rubber leaking grommet on the fuel heater. In your case , to do the same w/o the S. valve, I believe you'd need to crack the line at the ff output, enough to allow air to escape. Do it first when the engine is warm, to see what it 'should ' behave like first. Then re-bleed it the next morning. 5 - 10 pumps of my ball pump were typically required to get the overnight air out.

If you do confirm air in the ff, and there is fuel weeping out of the rubber grommet on the top of the ff, check on Youtube for a video about how to replace an IDI ff fuel heater O-rings. And ensure the ff's big rubber seals are tight too.

 

Thanks for the reply!

I do have the schrader (sp?) valve on the fuel filter head. It spits fuel like the dickens when I am cranking. Overnight it does seem to lose some prime. I get a whiff of air when I press it in without cranking and then it spits fuel when I crank it. I do not have the heating element and o-ring in my filter head like the 7.3s. I had a fuel line heater on the hard line from the mechanical lift pump to the filter head, but I have that whole line replaced with a clear one now (with the bulb primer).

When you pump your primer bulb does it seem like you are pushing fuel back through the return line, or actually into the IP? If you crimp your return line by the filter head, is it really hard to pump?

I do not understand why it will pop start no problem, but that I have to crank the bejesus out of it after setting over night. I wonder if I am not getting fuel to the IP when cranking, and that popping it uses the fuel in the pump enough to get it going, then it sucks through.

Thoughts?

 

This is my First time posting here so we'll see how this goes! I think my 83 is doing the exact same thing as yours. The only thing I haven't tried yet is roll starting it But there seem to be some sort of blockage at the injection pump. I'm getting fuel right up to the pump (with no air I might add) I even took the elbow off that goes into the pump and found nothing. I too have read about a filter screen somewhere but have been unable to find it. I've even looked at pump diagrams online and still couldn't find it.

I hope this doesn't constitute as hijacking a thread. if it does, my apologies

 

Don't worry about hijacking this!

Hopefully someone out there can help us out.

It seems to me that I can not push fuel through the IP with my bulb primer when I crimp off the filter head to injector return line.

I would be curious if you could get yours started by roll pop starting it.

Let me know if you learn anything else!

Cheers,
Ben in Maine

 

Note: The copper washers go under the fuel injectors to seat them into the heads, you only use those if you remove an injector - you then need to use a new copper washer when replacing the injector. They are not a part of the return fuel line system or related to air intrusion problems in the return fuel lines.

The Return Line Kit: That is probably the FIRST thing I would have done relating to your hard start issue. This is most often where the problems are. Air leaks in these return lines are often difficult to detect, and off the top of my head I think I counted 34 places where those return lines can leak and take in air causing the injection pump to lose prime. Counting each of the two o-rings on each injector under each cap (total of 16 o-rings, 16 rubber return line ends under the clamps on the caps, plus the 2 olive seals inside the compression fittings = 34 locations for potential and probable air infiltration leaks, if air infiltration is the problem.

The only sane way to approach it in my opinion is replace it all with NEW. I've read where people have hunted and pecked to fix leaks in those lines, replacing a couple of o-rings here and there and year later they are still hunting for where the leak is. Just replace it ALL and be done with it.

There is a long steel fuel return line that runs along the driver's side above the intake manifold going from the injection pump to the back by the firewall and there is a rubber "olive seal" on the end of that line inside the compression fitting. I'm not sure if there is an olive seal on the other end of that return line (at the Injection Pump) - I don't think so, but there is another olive seal at the FILTER end of the steel fuel supply line from the fuel filter header to the injection pump - under the compression nut. A good fuel return line kit should include those olive seals.

DON'T over-tighten the compression fittings! They can easily crack and then you are in a bad situation and would have to cut through the steel line to get a new fitting on it and then splice the cut steel line with rubber line and clamps or weld it back together. That would most likely happen if you are trying to tighten it to stop a leak caused by an old dried out, brittle or cracked rubber olive seal that no longer seals. Those fittings only need enough torque to compress the rubber olive seal, which is not very much at all.

Old rubber return lines can appear to be good but are old, stiff and even cracked under the clamps. Any of those conditions can result in air infiltration and not necessarily show a fuel leak (or one that you can easily see or locate).

The short fuel lines between the caps can be pre-cut to exactly 4 inches long (6 of those) and pre-clamped to the caps so one side with 4 caps can be installed at one time and all the 4 inch lines will be straight and neat.

Use a dab of oil on the o-rings before you slide them onto the injectors and into their grooves on the injector. The caps will slide on easier with no risk of displacing or causing any slight damage to the surfaces of the o-rings.

That would be 34 potential (and some probable) air infiltration problem areas that you just ruled out and eliminated.

In most cases that's what I would do before chasing any other possible causes.

 

I was very tired when I read (or tried to read) your original post and I jumped right to the Return Line Kit. I missed some important details in your post. Sorry about that.

First thing: Are your batteries good and strong, able to crank the engine over fast enough for a "cold start?" They also need to supply a lot of amperage to the glow plugs so if the batteries are not very good it will be difficult to start.

Secondly is your glow plug controller/controller relay and all glow plugs working properly??

From what you described about the push starts it sounds like it very well could be weak batteries and/or the glow plug controller/glow plugs! Especially since you are seeing fuel in those clear lines after sitting over-night. Of course it will start again with weak batteries, and/or with a bad controller or glow plugs after it's been running with a push start and the cylinders are warmed up. You could keep restarting it as long as the engine is warm enough. It might take two hours or longer for the engine to completely cool down.

Would it start on it's own again after 3 hours or 4 hours. If not, and you have not tested the glow plug system that's where I would go next. You really need to rule that out and confirm that the controller and glow plugs are working properly. This is a 1987 cab & chassis so it should have the Solid State Controller sometimes referred to as the 7.3 style controller. What is the Wait To Start Lamp showing? It should come on for at least 10 seconds, probably 12-15 seconds at the first cold start after sitting all night. Also you see the voltage draw on your voltage guage. From the first initial cold start through the after-glow cycle it could take a minute or up to 2 minutes in cold weather for the voltage gauge to come all the way up to where it should be.

If you are unsure about the batteries, have them load tested. The batteries should also have matching CCA Cold Cranking Amperage ratings and approximately the same Amp Hour ratings. (because) A lower rated battery will draw down the charge and performance of the higher rated battery. (In a perfect world where a person can afford to buy two new matching batteries:-)

I don't believe you can squeeze any fuel through the IP unless it is rotating. Fuel has to be compressed, (put under pressure) and injected out of each line in sequence under high pressures before more fuel can move into the pump.

I was going to ask what you saw in the replacement clear line from the IP to return fuel lines. I would expect that it should be full and not leak down because there is a brass check valve threaded into the pump at that line connection.

I was going to suggest that the check valve was dirty and leaking, allowing fuel to leak down and pull fuel out of the pump and some from the IP inlet fuel line but from what you wrote that doesn't seem to be the case.

For anyone interested: You can un-thread that check valve from the IP and clean it out by soaking it in a solvent like carbeuretor cleaner, or from a spray can and with a rag on a bench tap it onto the rag to shake the loosened crud out of it onto the rag. You'll have to do that several times until there is no more dirt coming out and possibly use a small tool to scrape some of it out or loosen it up. I have never done this before, only watched it being done in a YouTube video. A lot of crud came out of that one!


First, not dying again after a hard start does not mean it doesn't have an air intrusion issue. Especially when restarting it after it's been push started. However, I think weak batteries, and/or the glow plug controller & relay, glow plugs or the wiring to the above could be the problem.


IF it's not weak batteries and/or faulty glow plugs GP Controller/Relay or GP system wiring any of which won't allow a normal cold start after sitting overnight, then it sounds like an air intrusion issue.

No. I don't think so. The IP would have to be rotating. It's a high pressure pump that injects a pulse of fuel under high pressure through each line in series. Until the pump rotates and injects fuel into the lines more fuel can't be forced into the pump.

I think I've read where Macrobb has mentioned a screen somewhere in the pump but I don't recall where. I don't remember it from the injection pump manuals or in videos. If it was plugged how could it start and run fine after a push start, and then start up again normally if lines were plugged?

I'm not yet convinced that you don't have an air intrusion problem but I would go after the weak batteries and/or the glow plug circuit and rule that out.

All of my posts are "too long" but that's the only way I can write and be able to maintain concentration. (seriously) Usually late at night, very tired and with side effects of medicines I have to take 3 times day.

 

Fixnstuff,

Thanks so much for your response! I believe my glow plug system and starter are working correctly. I have the correct wait to start times and a good solid test light on all 8 glow plugs. They have been replaced within the last year. The batteries have as well, but I will check them on my buddies load tester today. Carquest has been good about replacing batteries if they don't last long. This is my second set from them. I am sure my battery cables are not pristine and perfect, but they seem ok.

Would it be the batteries if it takes a lot of cranking for it to start? It seems to me that because I CAN get it to start after so much cranking that the engine actually fires when the batteries are weaker than when I first try to start? Does this make sense to you?

I will go through my glow plug and batteries again today to rule that out. I thought I had, but I will check my voltage this time as well. I have a (hopefully) good quality return line kit coming from conestoga diesel and will put it in as soon as it gets here.

I have already replaced the rubber olives on the line from the filter head to the IP. I have the one for and will replace it on the back of the hard return line by the firewall today as well.

I thought I had already cleaned out the check valve on the top of the IP return line. I will pull it and use some heavy duty cleaner on it today as well.

I really appreciate the time and effort you put into these replies. It means a lot. I am trying to keep this old beast up and running as our farm truck and plow truck. I love the fact that it is all mechanical with not a whole lot of electrical and sensor stuff to keep it from running.

If I can get it a little more reliable my plan is to really fix it up with a new cab (the old one is totally rotted out), clean up the frame and get an inspection sticker.

Once again thank you for your help. I have intermittant and slow internet, so please don't think I am ignoring your help. I will keep updating progress when I get the time.

Cheers,
Ben in Maine

 

Sorry this post is so long again. I added discussion about the Fuel Shut-off Solenoid (FSS)

I hope you used Motorcraft/Beru ZD9 glow plugs. These are originally patented and specially designed and built for this Solid State Controller. The metal resistance bar in this controller reduces the voltage to the glow plugs down to 6 volts. The patents for these glow plugs which included mention of some special ceramic formulations and metal alloys which were not specifically named but the implication being that they were proprietary 'trade secrets' [the patents] expired, or were not renewed by BERU as of about 1997 - so other manufacturers can reverse engineer and duplicate them but did they? Some brands of after-market glow plugs may work OK while other brands have proven not to work OK and burn out quickly.

Measuring the resistance of the glow plugs with a volt-ohm meter while the engine is off is another way to test them. From the positive terminal to the grounded base of the glow plug (at the hexagon where the wrench socket fits) should read about 4 ohms. I'm not certain but I recall reading that 4 to 5 ohms is acceptable range. It might be slightly higher than 5 ohms.
Mine are 2-1/2 years old and if I remember correctly they read about 4.1 ohms a few months ago.

A half-bad, failing glow plug (even a BERU/Motorcraft gp) can be failing and yet still work but not correctly. It can still light up a test light although it would be dimmer if you can notice it. I had an old BERU gp like that. If you used Motorcraft gps manufactured by BERU (a German company) then I don't think you need to be concerned about the glow plugs since they all light up a test light. They should last for a long time.

Old battery cables could be a problem, especially if they have replacement terminals that are clamped or crimped on and not fully soldered. With so many copper wire strands in these cables, the terminal ends need to be fully soldered so all of the strands are making full electrical contact to the terminal. Then the exposed strands coated with "liquid electrical tape" (liquid rubber) or a good quality heat-shrink tubing to protect from moisture and corrosion between all of those wire strands. A build up of corrosion can result in increasing resistance in the cable which converts the current flow to heat and reduces the voltage and the current output. The voltage is a measure of the amount of force that is moving the electrons through the wire or cable and the amperage is a measure of the number of electrons moving through the wire or cable when a load is applied. This can also affect the adequate charging of both batteries. If I remember correctly, while engine is running, the charging circuit, measured at each battery's positive post to ground with a volt meter, should be from 13.7 volts minimum to above 14 volts, something like 14.4 or 14.5 volts. Above that indicates a different problem with the charging system but if you are down below 13.7, like 13.2 v. then it's probably due to bad cable terminals as described previously or a battery with a defective or failing cell (I think).

The key here is that everything electrical in the starting circuits (including glow plugs) is functioning properly AND the engine is turning over fast enough to start. Yes, it could be batteries but with regard to the power requirements not being met (if that were the case) I'm more inclined to think it could be related to defective battery cable ends.
If the batteries are not getting enough charging voltage and with the demands you've been placing upon them that's not going to help them last longer.

I don't know what else it could be other than what I've already discussed.

Hmmm. I was just thinking that if the Fuel Shut Off Solenoid (FSS) is not getting enough voltage during the attempt to start, it won't open to allow fuel flow from the Injection Pump. Then after the engine starts (push start) it does get enough voltage from the alternator to stay open and maybe for a few starts after that while the batteries still have a full charge.

The FSS and it's positive wire connector will be on the top driver side of the IP - the one toward the back - toward the fire wall. You can disconnect the wire terminal and clean the connection and then test it by jumping a single between the positive battery terminal and the spade connector on top of the FSS. You should hear a distinct click of the solenoid as soon as the wire is touched to that terminal. That shows that the FSS is working.

I don't remember what the voltage should read at the end of the wire terminal when the ignition key is in the 'Run' position. I'd have to look that up because some component circuits only around need about 5 volmayts. Since it's a solenoid it's probably designed for 12 volts. With a volt meter you could test the voltage at that wire terminal with the key in 'Run' position very briefly <-- Momentarily so not to drain as much current from the batteries while the glow plug circuit is energized.

If you see less than 12 volts at that connector that would warrant some further investigation and I could take the time to find that info for you.

About the FSS or wires going to any component, the connections made inside of plugs (connectors) or wire splices, (or ground wire connections) may be faulty, corroded or loose and not getting adequate contact which would create more resistance and may not transfer the full voltage and current required for the component(s) in that circuit to operate properly. That could cause an intermittent problem.




That back one in the steel fuel return line back by the firewall is an important one and also the one that people will skip most often when installing a return fuel line kit because it's difficult to access.

There is a mystique about these Ford IDIs that involves too many things for me to identify but I became addicted to my truck and passionate about fixing it up as soon as I saw a photo of it in an ad and heard it run and drove it the first time. I loved the sound and the sense of power from this V8 diesel, having loved diesel engines since the 1960's it's my first full sized diesel pick-up and turns out to be exactly what I was hoping to find with the money I had to spend. . I've become obsessed with fixing it up although it's been a slow project.

Just one more off topic comment: With regard to long term durability, high mileage and dependability, Your 1987 model year 6.9L engine, the last year of the 6.9L engines built for Ford, is the best 6.9L IDI engine that IH/Navistar had produced. It has a few features that make it better than previous years, two of which are roller rocker-arm assemblies and solid state glow plug controllers. It's also more durable than the 7.3L for a number of reasons that I'll avoid mentioning so as not to disturb the comfort of the 7.3L owners.

1987 was also a design change year, 8th generation (87-91) with changes in appearance outside and inside and it's a great looking truck!

If you are up to doing the work to replace the cab it's probably worth it.

 

Awesome info from fixnstuff!

Just in case your still interested, the filter screen that you mentioned is supposed to be located just inside the injector pump inlet. I'm not sure if it's just before or just after the fitting with the green o ring that the line connects to but I do know that you don't have to take the pump all apart to get to it.

I asked my brother about it and he said that he remembered taking the screen out of his old pump and putting it in the new one when he replaced it. For some reason the new pump didn't have the screen in it in fact, he had a spare pump laying around that we took a look at and that screen was missing as well so I'm not sure if the rebuilders don't tend to put them back in because they shouldn't be needed or what.

 

Restarting an old post but curious if you ever found a solution to your problem?

 

Those guys haven`t been around since 2017.

Charlie

 

From what I've read it seems it was glow plug related. Disabling the glow plugs and giving it a sniff of ether should rule out it being a fuel issue and point to the glow plugs.

These ip's do have a screen, but it's not really easily accessible although it's not too bad especially with the pump off. The screens are pretty big and I've yet to see one actually clogged up. It would take a lot to plug the whole thing and it would cause low power and possibly stalling while running it hard if it was clogged.

 

That was along the lines that I was thinking as well. Was searching to find an answer to whether or not an electric pump will push past the IP while engine isn’t turning. Got curious after reading through the comments.

 

I actually did figure out why it didn’t seem to be getting fuel. Turns out I was getting fuel through the pump,I confirmed this by removing the fitting from the return line on top of the pump then jumped the solenoid so I could watch it wile The engine was turning over.




I finally did figure out why it wasn’t getting fuel into the cylinders, turns out the various linkages under the top cover weren’t returning to the running position once the little arm on the shutoff solenoid retracted. So I got a clean screwdriver and moved the linkage around a bit until they started moving freely again. After that it was pretty much typical staring procedure for getting air back out of the system.

My best guess as to why the linkage wasn’t moving correctly is it got some gummy fuel in there from sitting so long.