Hello all, I have dealing with this problem for 4 months now. After the engine is warmed up and its really hot outside w/ a high under hood temperature I will hear the main fuel pump under the cab start making a lot of noise like it is cavitating and then within a few minutes the engine starts to stumbling and then quits.
I KNOW what the problem is as it happened when I had a fuel pressure gauge hooked up. The pressure starts dropping (when the stumble starts) and then it quits when the pressure gets too low. I can ground the test lead terminal and I can hear the pump start to work and then the pressure comes up. I can then start the engine. Sometimes it will run from that point on and not quit again, other times it will quit again. I can ground the test lead again, pressure it up and it will start again. It may, or may not, continue to run.

Now, if I walk away and come back after everything has cooled down it will start right up and I may not have any problems for weeks.

I have done the following.... I replaced the fuel pump relay, the EEC relay, the module on the distributor, new high pressure pump, new tank selector, new tank selector switch, new in-tank low pressure pumps in the main and saddle tank, replaced the ECU (computer) had 3 different ones. I have checked the ground wire at the battery box/radiator support. Added a 10 gauge extra ground wire at the same point. Added another ground strap from the frame to the engine.

I had a friend tell me he had a similar issue before on an E250 van and it ended up being the starter solenoid. I replaced the solenoid and made sure all the wires going to it were clean on the ends. After I replaced the solenoid the problem went away for the last month and a half. Yesterday when sitting in 100 degree traffic with the A/C on it started stumbling and quit on me.

If I were not dead in the water in the middle of a busy street I would have checked to make sure there was power going to the high pressure pump (brown wire), but I needed to get out of the street, so I grounded the test lead and once again I heard the pump pressure up the system. It started right up and and I got moving again, it then started stumbling and quit again!! I did however, have enough air speed to make a dead stick landing in a parking lot rather than being in the middle of a busy street. Grounded the test lead again and it started right up and I didn't have any more issues the rest of the day.

I am wondering if anyone thinks the fusible (spelling??) links at the solenoid could be the culprit? It is OBVIOUS that something is getting hot and causing the problem. The truck never quits when its cool outside, which down here at this time of the year is late at night or early in the morning. It is also OBVIOUS it is a fuel pressure problem and not an ignition problem. Something is getting hot and causing the fuel pumps/pump to shut off and then the main pump loses its prime. What is interesting is that I can ground the test lead and the pump will pick up the fuel and bring the pressure up to normal....

There are 3 connectors going to the starter solenoid. One is green (I think) and has a rectangular black plastic fusible link. The second connector has a cylindrical fusible link which has two yellow wires (I think) feeding into it. The third connector also has a cylindrical fusible link with two (looks like yellow) wires feeding it.

When the truck is running if I grab ANY of the connectors at the solenoid they are VERY hot! I don't think they should be that hot. They still have the heat shrink tubing on them, but they are STILL very hot. Do any of ya"ll think that the links could be the problem??? If they get really hot will they shut off the current to the EEC and Fuel Pump relays? I am not really familiar how fusible links act. IF, they are the problem, can I cut them out and put in a fuse holder on each one so I can use a normal plug in fuse? I could really use some help.... I have spend a fortune on this truck and I am still getting stuck. Thanks in advance

Scott In Dallas

 

Are the connectors too hot to hold on to for more than a second or two? Do you smell anything like burning or melting near them?

If they're too hot to hold on to, I'd advise replacing them. Or maybe try just replacing the fuses. It's possible a PO put the wrong amperage fuses in them. This can lead to the circuit tolerating a short because the fuse that's currently installed isn't receiving enough overload to blow. I don't know if the fuel pump has a safety shut off in case of voltage overload (it makes sense to me that it would), but if it does, then maybe that's what's causing the shut down. Then grounding out the test lead simply forces it to run.

But if this is the case, I don't know why it would work fine in cooler temperatures.

You might try cutting the heat shrink off and see if there's any bare spots rubbed through the wires.

I don't know if any of that is right, but it's all I have to offer.

 

Focus your attention on the ground side of electrical system.
To me, it sounds like a poor ground(s) somewhere/everywhere.....the extra ground strap (highlighted in red) won't be effective unless the ground from the frame to the battery is good.
A resistive ground circuit will heat up at it's weakest point (likely at the relays/solenoid)

Just my thoughts.

Bob

 

I don't see you changed the fuel filter. Try that if you have not allready did. Exact same thing occured on my F250 and was the fuel filter plugging up.

There is probly a small bit of crud floating around inside the filter and plugs up the last good part of the filter. When the engine dies, the lack of fuel flow will release that partical and your engine will start and run fine till that crud blocks that last good area of the filter. It will drive you nuts figuring it out thinking its electrical related.

 

Thanks Bob! I was unaware of the ground by the drivers side headlamp.. will check that out tomorrow

 

I did change the fuel filter.... can't believe I forgot to list it in what I have done. It was actually the first thing I did. Thanks for taking the time to reply I really appreciate it!

Only 3 replies from this giant bulletin board

 

I have to agree with eddie, my f150 would get super hot from running lean and I replaced most everything and still kept getting upset I was breaking down. my tank was dirty enough that the pump was unable to pump fuel (not all the time though, it was very random). had to replace the tank and pump and haven't had any problems yet. good luck!

 

Scott,

I took the time to go back and look at some of your posts from the past.

Remember this from 5/01/2013 :
"Yes, I thought it was the computer too. I bought a rebuilt one from the Official Ford place with a lifetime warranty and it runs worse now than when it had the original one. I also bought one off Ebay, same thing. So... it does the stumble thing with the fuel pressure drop with ALL 3 computers. It is also kicking off a bad O2 sensor code. Buying one of those tomorrow... Its only money, now have a grand in this thing trying to get everything fixed.... Thanks for the reply..."

As tough as this pill may be to swallow.......it sounds like a bad computer...AGAIN.
The computer is responsible for grounding out the fuel pump(s).
If there is a leaking capacitor(s), meaning the capacitor is failing, in the computer, they will cause intermittant stalls, no start, bucking problems.

Here's a read for you:
A9x ECM's (and same years ECM's) Failures Due to Age

And if you've got a thirst for knowledge, here you go (about 7K views of this thread):
//https://www.ford-trucks.com/forums/1183780-bad-ecm-or-dist-module.html


And now that I see you've got the 4.9 in your truck......all the more reason to clean the block ground (@ the starter bolt) and the cable terminal as well.

Did you ever find out where that mystery sheet metal box went when you changed out your computer ????
I'm thinking that was a DIY heat shield of some sort to mask the problem you're having.

Bob

 

Hi Bob, sorry for the delay in getting back to you.... Been covered up lately. I did spend all day cleaning grounding points. One on each side of the inside fender. The one/two wires going to the negative terminal. I have already cleaned the one going to the starter and replaced the cable with a new larger one. Do have another question if you have the time. I was checking the wires going to the starter solenoid. Have a green one with a fuse link going to the alternator. Have another connector that has a yellow and a black w/ orange stripe. And finally have 3 yellow wires...... One by itself going through a fuse link, two yellows going to one fuse link, and then after the three wires go though two fuse links it terminates as one connector. When the engine is running that one connector gets very hot to the touch.. not glowing or anything but I think it IS a problem. Thought it strange that two approx 16 gauge wires would go into a single fuse link and then one approx 16 gauge wire going to one by itself and then both having just a single connector. I was thinking that maybe there were too many amps having to go through the links. Was thinking of separating all three wires and cutting out the fuse links and putting a normal inline fuse on each and then giving each its own eye connector. What do you think?? Best Regards, Scott

 

Sounds like the fuse links are OK and normal. Upping the amps with fuses can cause a fire.

It may be the computer but since you have an I-6 engine they had a problem with this in the late 80's and Ford installed a fan and a baffle around the fuel manifold and up the fuel pressure to 60psi to stop the vapor locking. If you do not have this fan and baffle and the higher fuel pressure you may have a vapor locking issue.

 

Are the connectors at the starter solenoid supposed to get hot to the touch? I just don't understand how fuse links work. I have heard they can get hot and shut off the voltage? When I had someone tell me that I assumed as the fuse link would get hot it's resistance increased, which choked down the voltage. Since I am shooting in the dark, I just wanted to rule out one more possible cause to my problem. I want to replace the fuse links with the appropriate amp fuse. I have not been able to determine what amp fuses to go with??

My I-6 does has (if I remember) 50 psi of fuel pressure when running. I have the engine all original with the heat shield between the intake manifold and the exhaust manifold, the fan, with the baffle etc, and it does work. I did consider the vapour lock issue, and it does quit after it is good and hot. However, it quits even with the hood up and I would think with the hood up and 50 psi of fuel pressure it would not be a problem. I don't know..... It NEVER has quit when it is cool outside. Of course cool here is 70's in the summer. Every time it has quit on me it has been 100 (at least) outside, so God knows what the under hood temperature is. What is strange is how when it does quit, I can usually get it started again by grounding the test lead. I can here the pump pressure up and then I'm on my way again.... Just figured maybe the fuse links were getting hot. Is it possible to replace the links with an equivalent fuse?

 

May be the TFI module getting hot and failing. The short time its off it cools down and it works again. Without the TFI PIP signal to the ECU the ECU will shutdown the fuel pumps.

 

Is the TFI module the thing on the distributor? I have had problems with them before so it was one of the first things I replaced, if we are talking about the same thing

 

I have not heard that a fuse link will get hot and slow the flow of current.

A fuse link as far as I know when over loaded will burn in two and stop all current until it is replaced.

 

Hi Bill, Ok, sounds like they either work, or don't, just like a fuse. So, I guess my problem must be somewhere else. I will leave the fuse links alone. No sense in fiddling with something that doesn't need fiddling with..... Since I can rule the fuse links out, I guess my fuel problem is either a bad ECU, or just a vapour lock problem. Maybe one day if I can move from this miserable place to someplace cooler I will no longer have the problem