Intermittant, on start only, black smoke, low power, good idle, CEL with no codes.

[Hank]

Problem started today.

At first could not start the ex, cranked but would not fire.

Checked a plug, wet. Dried it off an put it back in. Waited for a few thinking it was flooded.

Cranked and it started, check engine light on, rough but holding idle. No power, bad smell and black exhaust.

About a min later I hear a deap phew or thump/whoosh may be a better description, cel turns off and truck is fine. Shut it down and start it back up the whole thing repeats but takes longer to come out of funky mode.

Side note here, when turning the key on, but not cranking, I hear the fuel pump running. Not just that 3-5 second priming but non-stop running.

Let it sit for a few hours with the battery cable disconnected and tried again. Same condition but lasted about 10 minutes, then funny deap phew noise and all normal. Let it warm up to normal temp as it is running happy then shut it off.

Turn the key back to on an the fuel pump does its NORMAL 3-5 second prime. Engine starts right up like normal, no CEL. Repeat 3-5 times when warm. All ok. Shut it off for the night.

Note, NO CODES being thrown when initiating an EEC test.

Checked the vac. tree and lines, all look ok.

Confirmed normal operation, voltage, resistance and proper movement under power, of the Idle Air Control valve, also cleaned it. Ex will stall when in funky condition if I pull the power to the IAC.

Thinking fuel pressure regulator or sticking EGR? What do you guys think?

 

[MrShorty]

"Thinking fuel pressure regulator or sticking EGR? What do you guys think?" What do I think? FPR maybe. I have not been able to confirm any case of a '91 having an EGR system, so I seriously doubt it's an EGR related issue.

Based on "Side note here, when turning the key on, but not cranking, I hear the fuel pump running. Not just that 3-5 second priming but non-stop running." and "Note, NO CODES being thrown when initiating an EEC test." I would initially suspect some electrical fault that is seriously interfering with the operation of the computer (and, as a consequence, the fuel pump, fuel injectors and everthing else).

When it's in "funky mode," do the injectors appear to operate normally, or do they appear to be stuck open? It might be interesting to see the fuel pressure in when in funky mode.

One clarification: when you say NO CODES, does that mean no codes whatsoever, or all pass (11) codes?

In short, I would work on figuring out why the fuel pump isn't operating normally, and see if that isn't the whole problem.

 

[Hank]

No codes at all, but then again the connector is really bashed up. Former owner or shop beat the crap out of it. Bashed and corroded eec connector.

Leaning towards pressure regulator myself. Could explain the constant fuel pump issue also.

Note that once it warmed up and "funky mode" went away the fuel pump behaved. Also gives a good case towares FPR which is a common item anyway.

Funny on the EGR, haynes sayes it is there but sure does not exist on mine...

Will pick up the FPR and fuel filter on the way home tonight. May have time to swap it out tonight.


Once funky mode goes away the rig runs perfect.. Also the pump behaves right at that point.

 

[MrShorty]

"Leaning towards pressure regulator myself. Could explain the constant fuel pump issue also" -- FPR has nothing to do with turning the pump on/off. It only regulates the fuel pressure once the pump is running. A bad FPR could possibly explain why the engine is "flooding," but it doesn't explain the fuel pump running nor does it explain why you aren't getting any codes.

I'm still holding out for some electrical fault.

 

[Hank]

Good point, now that I re-read it. If FPR was bad then can I assume it would always be bad?

This seems to be something mechanical or electro-mechanical.

Will need to clean up the EEC connector and see if I can get a real code.

May break down and get the actron code scanner for the first gen. 40.00.

 

[Hank]

Code scanner, 29.00 @ autozone, on hold at counter for pick-up tonight. Not buying anything till I can get a code out of this.

 

[Hank]

Quick update. Looks like 29.00 well spent. The actron scanner is a nice little test unit and the documentation is complete.

On the key on, engine off test I get a code 11

During the second phase of the test the timing is dead on

Third phase, second half of key on, engine on I got a code 21. Only once. Engine was in funky mode and once it warmed up and made the whoosh noise the code 21 never came back. Each subsequent test returned 11's

The haynes says 21 is the coolant temp sensor, acctron says depending on model is the CTS, coil or camshaft position sensor. I say the majority vote points to the coolant sensor.

Side info. Fuel pump is behaving. Forgot to mention, the radio is working fine now. Had the infamous ---

I quickly cleaned the connection on the coolant sensor and noticed the gauge was much more stable. Drove the heck out of it and it never moved off the O in Normal. Used to bounce around a bunch.

We'll test it again in the am when it is cooler but I think I have a bunch of bad connection issues. This all started after a full week of serious rain and major humidity. I have to go through some dirt and water to get into the office and I am sure everthing has been soaking wet for days.

 

[Hank]

No strange behavior this morning. Temp gauge relativly stable, "NO" range this am. This thing has always run on the cooler side of normal.

Will clean up and seal connections with dielectric grease this weekend. The thing is still dripping water in places from all the rain this past week.

 

[Joegun7]

Hey sry for the dumb question. One post said to clean or replace the "FPR". is it something to do with the Fuel Pump? And would replacing this bring back loss performance? Thx!

 

[MrShorty]

FPR=Fuel Pressure Regulator. Basically a back pressure regulator that controls the fuel pressure to the injectors. Excess returns to the tank.
Would replacing the FPR bring back lost performance? Replacing a bad FPR certainly would improve engine performance. Replacing a good FPR just for fun probably wouldn't be noticeable. FPR has three basic failure modes
1) Diaphragm ruptures and allows unmetered fuel into the intake. Remove vacuum line attached to FPR and check for gasoline. Gas = bad FPR.
2) Regulator holds pressure too high. Causes engine to run rich. Best tested with a fuel pressure gauge.
3) Regulator opens to soon, causing fuel pressure to be too low. Engine runs lean. Again, best checked with a fuel pressure gauge.

 

[Opera House]

Just one comment. The fuel pump relay has not been mentioned. Poor relay contact will cause reduced voltage to the fuel pump. This will cause lower fuel presure that will cause hard starting and poor running conditions. Contact resistance also causes the contacts of the relay to weld giving the pump run on condition. The welding of the contacts is a very known problem in the first gen. Something I would replace for less than $10.

 

[hermitrl]

Just a thought but check the vacuum hoses on the tree at the intake?Mine ran similarly when a hose fell off the back. Hard to see but easy to hear the air suction.

 

[Hank]

Thanks for the tip on the fuel pump relay. I think my case was water related, it did not rain the past few days. TS Arlene started dumping on us last night and already this am I had radio problems untill I ran the A/C on max to dry out the moisture in the cab.

When I say it is wet and humid down here, I'm not kidding...

There are some huge mud puddles and flooding already. Can't wait for my ride home

 

[Joegun7]

another dumb question im sure..

So whats the car going to run like if its a. too lean and b. too rich? Thanks guys!

 

[Hank]

Follow up post.

Looks like it was a flakey fuel pressure regulator. Never failed completly but was bad. This and a number of other odd issues were solved by replacing it.