Background:

Bought truck in January, check engine light was on. Drove it home and then straight to the body shop, so I haven't had a chance to diagnose anything. Just got home last week and getting into it now.

Brought it home from the body shop and it ran rough, barely made it home. Guy at the shop said it seemed to be running rich. Pulled the plugs and they did indicate that and I changed them. With the 'old' plugs, it woudl turn over, act like it wanted to start, but wouldn't. With new plugs, the truck popped right off immediately and ran great.

Fought to get codes out of it, none were stored, and only codes I got were 311, 538, 632. I believe 538 was considered human error, and 632 was as well because I didn't click the overide button since I figured out I have a short there that will blow the fuse and kill the code retrieval process.

Question for starters is this, will the Thermactor code cause the condition I have? Seems like it won't since the other symptom is when the truck get's hot, the trans won't shift properly. Won't kick down under throttle in D or overdrive, but seems to be ok in L1 or L2.

Thoughts and ideas would be so welcome, as the new plugs worked for a day and are now fouled out. Plugs/wires are new and will yank the plugs to clean them up tomorrow. All vacuum lines seem ok outside of a small white one on the passenger side of the motor. It's bundled with a red and black that go to the canister, but the white is broken off and not going anywhere. Also noted the gas line from the tank that crosses over in the middle of the truck (emissions) is rusted off, could that be an issue?

 

Dug into this a bit more today and the new plugs aren't fouled out, believe I have some other issue at play. Will be picking up a fuel pressure gauge to test that as well as checking out the TPS right off the bat. Assuming those check out, feel free to suggest the next path.

 

Have you tried a vacuum test?
Trans is E4OD?

 

No, but will be doing that. Have traced them down and only found 1 that's unconnected, but will to a test to make sure none are leaking.

Yeah, trans is the E4OD. What I've gathered from searches is it's probably acting up because it takes readings from the sensors, so hoping once I trace down my sensor issues that will fix itself.

 

I'd check your fuel pressure to begin with. A bad fuel pressure regulator can cause rich conditions.

 

Planned to do fuel pressure first, just didn't have a gauge until last night. It's 0, so I at least have a starting point. Had a new filter so planned to start with that, but the tool I bought is junk, so going to get something better. Changing filter first because I believe the body shop ran it out of gas, and since it's an older rusty tank, wouldn't be shocked if it was plugged. If the filter seems ok, plan to check to see if I have gas coming out of the return line to help troubleshoot the pressure regulator.

 

Does the pump prime when you turn the key? If it doesn't then the filter won't be the problem.

If the pump primes, push the schraeder valve on the fuel rail. Does fuel come out? If not then there is likely a restriction between the pump and the injectors; 1e. fuel filter, fuel pressure regulator.

 

The pump does prime, and when I put the jumper in the test connector, it runs. I just hooked the pressure gauge up to the schraeder, so assuming the 0 reading there shows a blockage?


Should also say I don't necessarily believe the 0 reading/no start now is totally related to running rich. Since i brought it home from the body shop, my symptoms have been different since dropping it off, so believe I probably have multiple issues. Hoping to get it running again today in order to keep diagnosing.

 

lol. Ok, so you can get better pressure readings when you have gas in the tank. It was completely out, and I haven't owned the truck long enough (or wrenched on anything for years since I've owned newer vehicles) to recognize a pump running dry vs with fluid.

When I dropped the truck off at the body shop in January it had 3/4's tank of gas. When I picked it up gas gauge was reading funny (way above F). Fuse was blown, and at that point went down to E. Put a couple gallons in it because I figured the grounding was bad (they pulled the box off at the shop) but it was so low at that point it didn't register on the gauge. When I talked to the body shop this week they told me they put 5 gallons in it because it ran out on them.

Long story short, body shop lied because the gauge is reading accurately and they didn't put 5 gallons in, and someone 'borrowed' the gas I had in it.

I just realized I didn't put at the top that I felt I had two issues because the truck wasn't starting at all now. First time it did that, I changed the plugs and it popped right off and ran good for a bit. Just happened it died a bit later because it was out of gas but I mistakenly assumed I had a more complicated issue.

I'm an idiot, basically, truck is running rich still but at least running, so I can now get back to my initial issue.

 

To update todays progress, after getting it warmed up I reset the timing and ran some more tests on it with my scanner. I did get a 173 code indicating it was running rich on the right side. Drove it for a bit to see if it would kick out a check engine light as it did on the way home after purchase, and it did, and it was the same 173 triggered during the KOER test.

Retook the fuel pressures after all of this because something seemed odd. Drove the truck and noticed it takes awhile for it to start once it's warmed up. Noticed that the fuel pressure is 45 psi with the pump running, but the second you shut it off it drops down to 0. Will be digging into that more tomorrow. Ultimately want to make sure I don't need a new fuel pump assembly before dropping the tank, which had been planned for the weekend.

 

To wrap this up, for now...

While the pressure test on the truck (not running) was within range, I did a test today with the truck running, and it jumped up to 90 psi. Did some testing recommended in the book to isolate the pressure regulator (as apposed to vacuum) and it seemed to be the culprit. Changed it out and the fuel pump test (engine off) pressure dropped from 47 to 45, and the running pressure went from 90 down to 35. Runs smoother and a similar drive to what would normally trip the check engine light yielded nothing.

Still have an issue with the pressure dropping to 0 as soon as the pumps turn off. Book recommended pinching off the supply/return line alternately to isolate if it's the check valve in the fuel pump or an issue with the regulator. Since neither made a difference, guessing it's an injector. Going to run some injector cleaner through it to see if it makes a difference (assuming it won't but it's worth a shot) and plan on possibly changing the injectors in a weekend in the near future.