Help on MPI stalling

Got the MOPAR FI kit on my CJ. I'm really pleased with the whole thing but I do have one small(ish) thing I just can't figure out. whenever I start it from cold (sat for more than 6 hours) I'll get a stumble followed by the engine quitting. This happens within 2 minutes of starting and then I can fire it up without incident afterwards. I'd say this happens 70% of the time. I've checked vacuum lines, retightened the intake and exhaust manifolds, and re-seated electrical plugs. Also, there have been no faults displayed by the check engine light....... I'm running stock champion plugs for an 86 CJ-7.

Anyone have any insight?

Thanks in advance. Rich Harris

Reply to
Richard Harris
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Mine will often die within seconds of starting. I did notice that if I was still in the habit of giving it a little gas before turning the key that it was more likely to die. It seems a little annoying, but overall the fuel injection is an incredible mod.

Jim

Reply to
Jim Meyer

Richard Harris ( snipped-for-privacy@san.rr.com) wrote on Saturday 23 August 2003 02:36 pm:

Rich,

I've got the same problem, and have been bugging Hesco about it off and on. He's given me a few hints.

The first one is on their hint page, and that's to drill a 1/16" hole near the center of the air intake flap (go to Hesco's web site for details).

The second was to make sure my distributor was centered. Turn the distributor left and right, marking the points at which idle becomes rough. Center the distributor between those marks. This didn't do me any good, and I put it back into its original position.

Check for blocked exhaust. I had a bad catalytic converter, but replacing that only fixed some horsepower issues during normal running temperatures.

His last suggestion was the adjustable fuel pressure regulator. That's probably what I'm going to end up going with.

I'm not blaming the MPI design for this, though. I had an issue with a bad rebuilt engine, and although it had a bad cylinder, it never died on startup. The second rebuilt I put in also did not have this problem. The third (and current) rebuilt I put in was the first to exhibit this problem. It's probably an issues of tolerances, not an issue with the MPI. BTW, the engines that had no problems were 84s. The one with the problem is an 81.

Good luck!

Reply to
Michael White

Mine does the same thing. It will start when cold and run for a few minutes, then the motor will speed up and die. The restart is smooth and problem free. It only behaves like this when I let it idle, if I drive away, it is fine. It is also fine if I wedge my rubber stopper under the gas pedal it run the idle speed up so I can use my compressor.

Reply to
Jeff Strickland

Not that it solves the problem, but that sounds like it's happening about the time the O2 sensor should be reaching a temp where the system goes closed loop. AIR, the MOPAR unit uses a heater on the sensor controlled by a relay and it determines the cold start switchover based on the output of the sensor OR a fixed time, whichever comes first. What you describe would be consistent with timing out before the O2 sensor reaches operating temp on the first pass, then actually reaching the proper temp and giving an output before it times out on the second pass. Other than a voltage drop in the wiring that keeps the heater from reaching the right temp, the only other answer would be a different sensor - a little expensive to try "just to see if it works" and it should set a code.

That's just some mus> Mine does the same thing. It will start when cold and run for a few minutes,

Reply to
Will Honea

I think I'll spend the money on more important stuff, and occasionally start my CJ twice. Thanks for the explanation though. Do you suppose my header could be playing a part in this? The O2 sensor should be installed in a collector where all of the tubes come together, but my senior-moment-plagued mind's eye says the sensor is in a collector that only looks at one set of tubes. My header is a 3 into 2 into 1 design, and logic says the sensor should be in the 2 into 1 collector, but I think it is in one of the 3 into

2 collectors. I don't really care if the sensor looks at all of the exhaust gas or not, but I wonder if the header could actually be cooler than the standard manifold, and keeping the O2 sensor from getting hot in time. You did mention the manifold heater, but that is contained in the carburator manifold, not the fuel injection manifold. Hmmm ...
Reply to
Jeff Strickland

Jeff, I think I'll do the same. Everything is fine after the initial stall and the annoyance isn't all that bad. On the other hand I'm just a poor sailor and to me we spent a pile of bank on this system, it should run right. Jeff, about the header thing, I'm running a stock exhaust manifold and my symptoms are there, so I think it could be something other than the header. Rich

senior-moment-plagued

Reply to
Richard Harris

I would probably put up with, too. That's about like my 88 MJ: start cold, use the tranny to hold the speed down descending the hill by the house and the damned thing will die 8 times out of10 when I stop a the bottom of the hill on the first start of the day. It took months to get all the problems with the idle straightened out when I first got the thing so I just put up with that little quirk.

The heater I was taking about is on the O2 sensor, not the manifold. The only preheat I know of with FI is the one on the air intake port and you know what that does to you.

I'm trying to remember where the O2 sensor is on the stock HO engine. On mine, it's just above the flange at the very end of the header which makes sense to me. Wonder why they put it where it only sees two cylinders worth of exhaust?

Reply to
Will Honea

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