Hello everyone, I have a 1988 f150 with the 300 inline 6, I bought it being a “new truck” with the parts cannon already thrown at it, and some iffy wiring but it ran and seemed to drive okay and the price was right enough so I bought it. Glaring past the obvious issues, everything seemed fine and I didn’t get to drive it enough for the real issues to come about. On hot start it revs to 2-2500 depending on what it feels like and drops right back down, I’ll admit that I should have tried to do more diagnostics but this system seemed simple at first glance and a faulty iac seemed to be the issue. I know cheap parts store brand parts are known to fail so I replaced the iac, tps, coil, and eventually the distributor with motorcraft parts. Problem still stayed, fairly disappointing but it was still driveable for short trips until it started seeming very doggy and breaking up at some points. Throw the scanner on it, I’m getting egr codes which makes sense, it has a new egr and sensor but they’re non functioning since the rest of the smog has been hacked off poorly, and A code 95 for a secondary fuel pump circuit fault. My high pressure pump on my frame rail never shuts off, I started digging into it but I’m not very good with wiring or early computer controlled stuff. It’s also hard to follow because someone else has been here before me. The fuel pump relay was completely corroded shut and wouldn’t work, I thought this was my saving grace but my fuel pump still doesn’t shut off. I should mention that it started leaking fuel from the selector valve, I thought this might also be the issue, maybe it’s sending gas to the other tank sometimes and that’s why it starts running bad? It seemed to not break up but was never right. I made sure to get the $300 Ford piece of plastic and it’s not having any leaking issues. I continued to drive it to work not having much other option, and it shut off randomly. Started back up and drove me home. This was before I discovered the relay being an issue. Drove it for almost another tank and it shut off again. Didn’t start up first try, ran the second try and made it another 3 miles where it didn’t fully shut off this time, I pressed the clutch in and it would barely stay idling but wouldn’t rev. I’ve yet to drive it but have ran it for 15 minutes and checked on things and it didn’t shut off but still revved up on restart. Any help would be greatly appreciated, selling it for a loss is seeming more and more like my best option. Thank you

 

My thoughts now are that the fuel pump isn’t grounding thru the computer, does anyone know why there’s two wires spliced into one and why the inertia switch is spliced out of another? The fuel pump relay plug has been replaced with different colors but I was able to verify that that is all hooked up correctly

 

If you are not getting any other codes, I would pull the PCM and visually check it for bulging and/or leaking capacitors. I would also get the numbers off the PCM and make sure you have the right one. It can be verified here on the forum. At least you can get this major component out of the way if all is well.

 

pcm has been replaced with a brand new one, the plastic cover has been off before me and there was a junkyard computer already put in. I wish the guy was honest and told me the full story it might have helped me solve the issue sooner and cheaper.

 

OK. The PCM you got should be for a manual transmission. There is a difference.

 

I know, it’s the right computer. With the wrong one it wouldn’t run or do anything, I don’t think an auto trans computer would cause these issues either

 

I doubt it would either but.... Just making sure you are ok with it since you are having issues. Did you run the Key on Engine Off diagnostic test?

 

Tested fuel pressure, has 42 pounds and holds it, goes up by 2-3 psi with slight throttle, doesn’t leak at all. While it was running I bumped my turn signals and they decided they don’t work anymore, and it no longer will crank. This has to be a wiring issue but I don’t know where to start, the relays all click like they should, how does the main high pressure pump ground thru the computer? Could it not be and that’s why it always runs? Is there a bad wire somehwere and that’s why it shuts off?