Yesterday I got in the truck for the first time in a week. It started up and ran great until I made it about a mile away from home. Then it started running very poorly and the MIL came on. The motor seemed to only be running on about half of the cylinders and was shaking and skipping. I limped it back home and started looking at it today.

First thing I noticed is that when I turned the key to start to read the codes the fuel pump came on and would not cut off. I tried both tanks same thing. I pulled the battery cable and let it sit a few minutes and reconnected it. After that I tried again and the pump came on for a couple seconds and cut off like normal. I went through checking the codes with my Innova tester and only got a 111-10-512 before the tester hung up and the fuel pump cut back on and would not go off. Code 512 is listed as Keep Alive Memory test failure. I swapped the fuel pump relay with the horn relay and nothing changed.

A few things of note on the truck. It is a '94 but has the grey ICM. I read in another post that a '94 should have a black ICM. I have had the truck less than a year and it has randomly ran rough and generated MILs a handful of times. But every time it would stop and the codes clear on it's own in a couple seconds or when I cut the truck off and back on it would be fine. I was never able to retrieve any codes from memory afterwards.

What should I check next? I'm having a hard time troubleshooting since I can't get the codes.

 

ICM is a problem but not directly related to the fuel pump --- did you pull and reset the EEC power relay (a hang up here can create fuel pump relay issues)............?

 

Which one is the EEC power relay? I only pulled the fuel pump relay and horn relay and swapped them to verify the fuel pump relay was not sticking.

 

Just behind the air filter......to the right of the VIP test connections on the fender mount

 

 

Fuel pump continuing to run beyond timed cycle and coupled with basically runs like crap sounds like a PCM issue.

Fuel pump run key in run position is a timed thing, computer controlled.

Might wanna pull it out check for obvious signs of trouble, bulging and or leaking capacitors.
A fairly cheap and simple fix if caught early on, all caps replaced before the board itself is damaged beyond repair due to leakage.

 

Exactly -- the EEC relay or PCM can produce these very issues......

 

Thanks guys. I will check the EEC relay and pull and inspect the PCM. Any tips for pulling the PCM?

I'll get back on this tomorrow after work. It's getting dark.

 

Got the PCM pulled a few minutes ago. It has some swelling and leakage on the capacitors, but most of the ones i've seen posted on here are worse. What do you guys think?

Sorry about the lousy pics. I suck at photography.

 

There's the problem, some are leaking into the PCB.

 

The caps that are leaking need replacing. This is one of the 2 main problems on ECUs, the second is that the phenolic board wicks moisture slowly over time, this can be dried out, these two items fixed and the ECU hopefully will operate correctly.

 

Looks like they've been replaced before -- they're a high failure item on PCBs and the swelling observed is typical due to the repeated heat/cold cycles they go through...........

 

"Looks like they've been replaced before -- they're a high failure item on PCBs and the swelling observed is typical due to the repeated heat/cold cycles they go through..........."

What makes you think they've been replaced before?

 

Can't tell extent of damage pictures are kinda blurry, I'd take it to a local electronic repair shop have them give it the once over.

I took mine to local tv repair shop, he replaced the caps all three of them for 20 bucks.

Can do it yourself if have or have access to the couple specialized tools required (getting the old caps off is the hard part), replacement caps are easy to get regardless who fixes it.

 

I got the refurbished PCM installed today. I just got back from a 20 minute test drive and it ran great!

I'll probably change out my grey ICM for the correct black one in a couple weeks. I want to make sure this issue is fixed first.