1994 Lightning starting issue

M

MGAJIM

Registered User
I Support the NLOC
Gentlemen,
I went for a ten minuet drive and truck ran fine as always. Returning home I started the truck and it started fine and ran about three seconds and shut off. Turning the key, there was no pump buzz sound or starting. I checked the 20 amp fuse in the engine bay that is good and the inertia switch that is still depressed. Six years ago I had replaced the rear tank and reused the original pump that has run flawlessly since then. I had removed the front tank back then and blocked the lines. Foolishly I just replaced the 30 year old pump with a new NAPA Bosch pump and still the same thing. No "buzz" or fuel pressure at the rail. What am I missing? Thanks!
 
MGAJIM said:
Gentlemen,
I went for a ten minuet drive and truck ran fine as always. Returning home I started the truck and it started fine and ran about three seconds and shut off. Turning the key, there was no pump buzz sound or starting. I checked the 20 amp fuse in the engine bay that is good and the inertia switch that is still depressed. Six years ago I had replaced the rear tank and reused the original pump that has run flawlessly since then. I had removed the front tank back then and blocked the lines. Foolishly I just replaced the 30 year old pump with a new NAPA Bosch pump and still the same thing. No "buzz" or fuel pressure at the rail. What am I missing? Thanks!
Click to expand...

Does the truck have a chip? If so remove it and then try again. Also while you have the computer out you'll want to inspect it for any leaking capacitors or other issues.
 
Check the relay. I would start by simply bypassing it with a jumper wire to see if the fuel pump runs. If the pump runs, then you can check the signal to the relay to make sure the relay is being told to come on. If it is throw a relay at it. Or if you're older like some of us and your time and effort is worth more to you than an $8 relay, just throw a relay at it and see if it fixes it.
 
Thanks Oilwell,
I fit the old category as well as electrically challenged so a replacement relay is next.
 
See if you're getting power to the relay. A test light will tell you if there's voltage there, but you need a load to see if there's good power. An old sealed beam headlight works well for that. If you've got no power at the relay you'll have to trace it back to the last place you do have power. I suspect you do since you said the fuse is good.

And I'm going to throw out the obvious just in case it isn't so obvious. You didn't accidentally flip the tank selector switch to front did you? If not and if you have power at the relay the fuel selector switch is the next stop. It's been a minute, but IIRC you should be getting power into the switch on a red and yellow wire and power goes out to the pumps on a brown wire and a red wire. Don't remember which one went to which pump.

Actually, I think I would start at the selector switch. If you've got power there you know you've got power to the relay. Probably should check to see if the relay is being told to come on by the EEC. If not it could be the EEC relay.
 
After reading the OP again, I suspect you got a bad fuel pump or there was an issue with the installation. I'd double check that. Another thing you can try is hitting the bottom of the fuel tank with a rubber mallet while someone cranks the truck. That will sometimes unstick a bad fuel pump. It's gotten many people home and saved a tow bill.
 
Oilwell,
I checked for voltage back at the pump and it shows nothing. And also checked for spark at the plugs also showing nothing. Starter cranks fine but neither fuel pressure or ignition. Does this sound like the electronic engine control or power control module has failed?
 
Sounds like an EEC or EEC relay issue. Could also be something as simple as an ignition switch not sending the juice out.
 
Hall effect sensor will also impact both spark and fuel, but with the fuel pump not priming, it sounds more like something associated with the ECU. I'll second the EEC relay thought since the ECU very rarely dies that suddenly and completely.
 
Gentlemen,
Key on there is power at the coil but no spark or fuel pressure. I could jury rig 12 volts to the new fuel pump to see what effect that would show. I'm not completely understanding FMOS suggestion of distributor Hall effect possibly causing both spark and fuel issues. I just watched a Youtube vid showing a fella with a similar year F150 problem finally replacing the computer and resolving the issue. Ford parts doesn't show a replacement ( maybe obsolete). Internet prices are wildly variable, but might you have a reasonable suggestion and is the Lightning variation important? Thanks!
 
There are at least two ignition outputs from the switch. It's possible that one powers the EEC and the other the ignition. I don't believe the ignition power goes through the EEC circuit.

The Hall effect sensor is the part of the distributor that determines when to fire the coil and injectors. If that signal is not getting to the EEC it will not trigger the spark or injector pulse.

The computer is Lightning specific and they are getting hard to come by. I would not just swap it until you are out of other options. If you just wanted to see if changing it fixes things you should be able to swap in any F series computer from around that year and see if the fuel pump kicks on. The engine should probably start and run with any V8 computer, and may run even with the 4.9 computer.

Since you have two good fuel pump relays, I would replace your EEC relay with one of them and see what happens. If it doesn't fix it you'll need to check the relay connector to make sure it's getting power where it should be getting power. You could even install a jumper to see if that gets the truck running.
 
Either way removing the ECU to inspect it is a good idea. Like Ray said they are prone to pop capacitors and cause seemingly random and unrelated issues too long to list. You’ll either find it has already been repaired or will need to be.
 
Gentlemen,
I removed the computer and it is seriously fried. The backing cover plate has soot on it so some unidentified parts got hot enough to burn. Ford parts does not show a CPU available for a 1994 nor does NAPA parts. Any suggestions as a reputable parts source? I certainly appreciate all you guys incites and comments.
 
Gentlemen,
Ray had it right and just out of curiosity, what might cause a overheat situation with the computer? It is confined in a air tight space, where as the Ignition module is in the open with a heat sink base. Just curious.
 
It's just old. They all eventually pop the capacitors.

Regarding the hall effect sensor, if there isn't an RPM signal, there isn't a spark trigger, and the ECU won't fire the injectors or run the fuel pump beyond the 2 second prime. That's just for the sake of explaining. Obviously not the problem here!

I have a C3P1 laying around. It works well enough to run, but has an intermittent CEL for O2 sensor and will run roughly when that comes on (I think it's running lean, and the O2 sensor CEL is legit). I replaced the capacitors on it, but that didn't solve the problem. However, one of the professional EEC rebuilders may be able to salvage it.

I've converted both of my trucks to the Stinger ECU.

Does your truck have an E4OD?
 
Yes, it's the normal Ford automatic transmission that's never been touched.
 
Gentlemen,
One last question. Would any other Ford computer get the truck to run again? Thanks for all of your suggestions.
 
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