Hello,

I browsed back through several months of posts in this specific forum but did find answers to my problem(s). Not that I'm complaining-- just saying that I have tried to find relevant previous threads before posting my questions.

1987 F150 302 EFI with 110,000 mi

I've owned this truck for only about 18 months. Shortly after I bought it, the fuel pump relay switch failed. The pumps would not run when ignition was turned on to 'prime' the system, but some amount of cranking would start the motor and once running it would run fine. I replaced both the fuel pump relay and the EEC relay. This fixed the problem and the motor ran flawlessly. The 'engine' warning light on the instrument panel does work but was never on while the motor was running. Ran great for almost a year until one day last week. When started up cold that day the motor ran fine for about 20 seconds then died. (Both tanks were more than half full and it had been running fine on that same gas from the last fill-up.) By turning the ignition key on and off a few times to cycle the pumps I got it to run again several times but only for about 5 seconds each time. It sure appeared to me to be running out of fuel as opposed to an ignition failure because it would 'try' to run and stumble along before finally dying.

At this point I decided to start replacing parts. Before I get accused of being a knee-jerk reaction 'parts replacer' hear me out. The truck has 110K mi. and the in-line main pump appeared to be the original. The rear in-tank pump was starting to make a terrible racket and I was planning on replacing it soon. The front in-tank pump seemed to be working OK but the sending unit was completely dead. (I had previously taken the pickup assembly out to bench-test the sending unit to make sure). So I essentially had two junker in-tank pumps and one 18 year-old / 110K mi. high pressure pump. I did not see any sense in spending any troubleshooting time on worn-out junk pumps. Even if I was to have found the real problem by diagnosing everything I would have still had a worn out fuel supply system on its very last legs. On the other hand I didn't have any great expectations that new pumps would fix the stalling motor. I just saw it as a maintenance move that might on a long shot fix the problem. It didn't.

I installed all three new pumps, a new inline filter and a new fuel pressure regulator on the fuel rail. The motor still stalled but could be restarted only to die again just as described above. I checked all fuel lines for kinks or damage. My code reader showed no error codes and showed a 'pass test' on both Key On Engine Off Self Test codes and Continuous Memory codes. I removed the fuel line from the inlet (rear) of the in-line pump. Both in-tank pumps will pump fuel out the tanks, through the lines, through the fuel reservoir unit and out this open line during the 3 second or whatever 'prime' period as well as during any starter cranking. Test lights attached to pump + and - wires show that current is present at all the pumps during the 'prime' period, during engine cranking and after the motor starts and even after it begins to stumble and misfire. Current finally stops a second or so after the motor has completely stopped.

So what is next? Check fuel pressure at the injection fuel rail? Since the motor will not run long enough to do that, what is the process? The Ford manual leaves a lot to be desired for troubleshooting this sort of problem. It does describe modifying a fuel pump relay to force the pumps to run continuously but-- I need to waste a relay to do that??? Or is there another way? Is there a port or connector on the fuel rail to attach a pressure gauge to? Is there any way this could be an ignition problem that acts like fuel starvation? Wouldn't most ignition problems with this system simply prevent the motor from firing at all?

Thanks
Dave

 

This afternoon I disconnected the fuel return line all the way back at the frame-mounted dual tank fuel reservoir. I connected a temporary hose from the end of the return line into a bucket. I started the motor -- remember it will fire up but will not run for long. During the brief time that it will run a good steady stream of gas comes out the hose. While this does not tell me I have adequate pressure at the fuel rail, at least it tells me the pumps are pumping fuel in a full circuit at a good rate.

Does anyone know of any detailed troubleshooting info online for EFI?

Thanks for any suggestions offered.
Dave

 

A fuel pressure gauge would be the first thing. That way you can eliminate either fuel . yes, there is a fitting a on the fuel rail for the gauge. The fuel lines are usually pressurized. The way you said about turning it off and on a few times, says its losing pressure somewhere. But if this happened after you took things apart, it would be normal.

 

I purchased a pressure gauge with the appropriate Ford fittings, found the port on the fuel rail and hooked the gauge up. When I turned the ignition key to the 'run' position to cycle the pumps, gauge pressure jumped to 40 psi and stayed there. When I cranked the starter and the motor fired up pressure dropped to 32 psi and stayed there until the motor sputtered and died. I repeated this test three times with the same results. I also turned the ignition key to the 'run' position so as to achieve 40 psi, then turned the ignition off. I left it off with the gauge pressurized and the system held the 40 psi indefinitely.

In going through the above sequence of events a couple more times I made a new discovery. If I start the motor up several times after it proceeds to cough and die, then let it sit for a few minutes, then try it again-- it will start up and run fine as long as I want to leave it run-- as if nothing at all was wrong. However, if I then shut it off, let the motor sit and cool down for even 15 minutes or so, then try to start it again it is right back to the sputter and die mode. When this is occurring, the fuel pressure test gauge still shows 32 psi as the motor is coughing and dying. It will even jump to 40 psi as the motor finally stops tuning. I assume this jump to 40 psi is because the pumps run a very short time after the motor stops running.

Dave

 

Thanks for the response 220k-f-150 !!

I just posted my pressure test results. Thanks.

 

Doesn't sound like fuel delivery problem. Since your not getting any codes I would suggest IAC valve. Take it off and use carb. cleaner to clean it out. Also Check the connection to the valve. They get build up in them and they stick. Also your manual has specifics on how to test it for voltage and such. Usually a good cleaning will get it going again. Or since your on a replacement role, maybe a new one. I'd try cleaning first.

 

ok, shot in the dark but here me out. have you replaced the cartridge filter just behind the high pressure pump? it is called the fuel reservoir.....had same prob that fixed..about $5

 

86Bronco

I'm not neccessarily familiar with the setup on an '86 Bronco, but my understanding is that on my dual-tank '87 F150 the 'fuel reservoir' is not a filter. It is a pressure-differential diaphragm-operated valve used instead of a 6-port electric solenoid-operated tank switching valve. No filter is associated with it. It is quite expensive to be purchasing just for the heck of it. My cost is about $77.00 at Ford. On the other hand the high-pressure in-line cannister-style fuel filter located ahead of (downstream of) the high-pressure in-line fuel pump is something I did replace when I replaced the fuel pump.

Never say never but I think I did more than likely eliminate the fuel reservoir as the culprit by my test described in a previous post. Meaning-- where I was able to pump fuel through the fuel reservoir with both the front and rear in-tank pumps. In fact at one point I removed and disassembled the fuel reservoir to check for dirt or other debris. It was very clean. I could not see any obvious problems and the tank pumps are able to pump gas through it.

 

220k-f-150

I had high hopes about your suggestion on the IAC valve. I took it off. It was a little sooty but not stuck or inoperative. I cleaned it out and made sure the solenoid motor was working. The cleanup had no effect on the engine stalling problem. In looking at the IAC valve in comparison to the stalling problem I would estimate that the problem is of a much more drastic nature than what a malfunction of the IAC valve could create. When the motor first starts up it does not misfire or stumble at all for a few seconds. It sounds great. Then-- kapow! Instantly it is as if the fuel supply is gone and there are only a few more cylinder explosions left to keep the motor turning for the next few seconds. If I had to equate the stumbling effect to an excess of air (meaning a huge vacuum leak) instead of a lack of fuel, I'd say it is the equivalent of a much larger 'leak' than the IAC could create. Even at 2000 RPM, once the motor starts to stumble, that's the end of it. Its gonna die soon. Nothing done with the throttle or whatever will cause it to recover. Its only by repeatedly re-starting the motor that it ever reaches that zone where it does not stumble and decides to run any length of time.

 

Ok, I get what your saying, but remember that its computer controlled. To get the carburation effect, all of these sensors and such have to work in unison. I went with IAC valve because of no codes. With the IAC valve the computer operates it, but once it gets mechanical part of working, the computer don't know if its working or not.
The NO codes is what got me stumped.
We have eliminated fuel pressure, because it maintains 32psi as its dying. We eliminated IAC valve, with your cleaning it and checking it out. I would check the TPS and MAF sensors, also. The TPS (throttle position sensor), does reset every time you turn the igniton off. So maybe that. You might go ahead and clean out the throttle body. Some people take it off, and other use a throttle body spray. If you use the spray just don't use alot at one time, and make sure vehicle is running.
Here is a shot in the dark one, take neg. wire off of battery for 30min or so. Maybe glitch in computer. Its worked for others.

 

>>>The NO codes is what got me stumped.>>>

Meee to-- as if I wasn't already stumped before that point. But I'm pretty sure the scan tool and the dash light warning are working. If I unplug a harness connector from some component and run the scan again it will show some error code(s). If I plug everything back together and re-scan it shows no errors again.

I decided to remove the throttle body so I can clean it very thoroughly. I may just replace the TPS on the thought that it may be erratic from the 110K of service. That and having the TB off for cleaning would definitely be the time. The dealer did not have TPS in stock-- will have one tomorrow if I want it.

There have been several times when I've had the neg bat terminal off for several hours while working on the fuel system. It has had no effect on the problems.

 

Got the throttle body off and cleaned up. Tested the TPS with an ohm meter. It did not seem to be erratic or otherwise malfunctioning although I don't know what range of resistance it is supposed to have. As I rotated the throttle, the resistance change was very progressive and consistant. It does look like the original though and is quite crusty. I'm thinking I may wait for the new one tomorrow and try it instead.

As I was pulling the TB I kept looking at the TFI ignition module wondering if I do have some kind of freaky ignition problem that acts like an EFI problem.

 

Just looking ahead for likely next steps....

Is there a tester for the EEC computer itself? Meaning, can I take the computer out of the truck and have it tested? Or would I run into the same situation as with a TFI tester? I've read that a TFI tester can only give the module a 'good' or 'bad' rating. It can't be used to verify anything regarding an intermittant failure which of course is exactly my problem. Intermittant failure.

 

Correction to my last post. The MAF should be MAP (Manifold Absoulute Pressure) sensor.
The TPS voltage, with key on should be .05-1 volts, Then wide open at 4-5 volts.
The IAC voltage, with key on should be 10.5.
The MAP voltage, I usually just replace it, but manuals show detail test.
Might even try O2 sensor, and maybe follow all wires to computer check for bad connections and such. At this point I can't deny that it could be electrical (TFI). But MAP does work with ignition timing.
I am still thinking of the no code situation, could it be possible clogged cat. converter?
Since you can start it and it will idle, it does sound as if the EEC is changing something to make it lean or changing timing. For the computer to change, it may getting a bad reading from one of the sensors.

Although, we seem to be getting plenty of fuel pressure, try this, when it starts to die pinch off the fuel return line a few seconds and see if it improves.

Anybody else out there have this problem, with no codes?

 

Got the new TPS. Bench test compared it to the old one with an ohm meter. Values were very similar so the old one is probably still OK. But as I alluded to before, it didn't make a lot of sense to me to have the TB off for cleaning and not replace a very old TPS. Installed the new TPS to TB and installed on motor.Tested TPS voltage-- is to spec.

Voltage test after new TPS installed
Supply voltage 5v
Closed throttle 0.82
WOT throttle 4.52

By this point I was 99.9 percent certain this was not the fix but went through the motions-- started the motor. Same results. No change.

I could not find procedure for MAP electrical test. I had previously pulled the MAP connector off to see if that made a difference as far as running the motor. It did not. I installed a new one from NAPA as Ford was out of stock. Same results. No change in how motor runs. No error codes.

>>>Since you can start it and it will idle, it does sound as if the EEC is changing something to make it lean or changing timing. For the computer to change, it may getting a bad reading from one of the sensors.>>>

This is what I always come back to as well. As it is sitting there idling for the few seconds that it will -- whether on fast idle at 1500 or normal idle at whatever-- everything is absolutely fine. Then just instantly-- something changes. Instantly. But the motor attempts to keep running, its just that it can't. It is not as if the ignition is completely shut down either. When it stalls the motor does not shut down gently without a fight-- as if the key had been turned off. I have the truck on my floor hoist about 12 inches off the floor. When the motor stalls out it, is bucking and kicking around on the hoist. It does not do that if you just turn the key off while it is running. After it starts bucking you can make it stop doing that by turning off the key. It just seems the computer is telling the ignition, the timing, the injectors or whatever to do something that the motor cannot accomplish. (That is still not to say that it couldn't be an intermittant TFI problem that the EEC can't correct.) Combine all this with my previous post where I describe that if you keep trying, eventually there comes that time when it will fire up and actually run normal for as long as you want it to-- if you don't shut it off. Heck last time it did that I drove it out the shop and around for about 5 miles. Parked it back in the shop. Shut it off. Started it up. Ran fine. Shut it off and let it sit (and cool down?) for 10 minutes. Started it up. Right back to the same old starts-but-won't-run stalling out routine.

>>>For the computer to change, it may getting a bad reading from one of the sensors.>>>

Or from itself? Internal problem in the EEC? Would/would not this show an error code?

>>>I am still thinking of the no code situation, could it be possible clogged cat. converter?>>>

Well, it sure was not high on my list of things to check. Here's why. I use this truck to work on my house. It has a big, long lumber rack that extends well out in front of the windshield, a table saw, several heavy metal work stands, a fair amount of misc stuff, a large Delta toolbox full of carpentry tools, and usually two full gas tanks or at least half-full gas tanks. I've actually weighed all of the tools and stuff and depending on what all is there at the time it is 1000 - 1200 lbs. When I leave the shop to work on the house I go up a very steep freeway entrance and accelerate from a 25 mph 180 degree corner up a hill to 60 mph-- with this weight-- with the 'big old air brake' of a lumber rack. For what it is -- a small block in full-size long box truck-- it boogies along pretty well and did the day before this stalling all started happening. Granted, its not my built '70 429 C-6 Ranchero in first gear up the same hill, but I find it hard to believe there is any great amount of exhaust restriction. Having said all of that-- perhaps if the converter is restricted to some threshold value that doesn't hurt performance but does mess up the computer????

But before removing the converter -- don't I have the O2 sensor to check? and maybe an Air Charge Temp sensor? I assume this has an ACT but don't know where it is located-- the manual I have does not say where it is. Also have not been able to find voltage or ohm figures for testing the O2 sensor.

Won't pinching the plastic return fuel line kink or crack it?-- remember it is 18 years old.