Update!!!--MPI DOESN'T WORK--PLEASE HELP. - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 06-12-2000, 05:43 PM
Robert87yj
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Update!!!--MPI DOESN\'T WORK--PLEASE HELP.

I have been fiddiling with this MPI for a few days now and can't figure out why it doesn't run. It is acting like it is a timing problem. It sputters a little and doesn't start. I checked all of the timing, clearances, etc. to no avail. but I did find one thing that might be the problem. The lead to each injector is always hot-EVEN WHEN THE KEY IS OFF???. This doesnt' make sense. Don't efi injectors open when voltage is applied? The injectors aren't supposto have voltage all of the time are they???

IF anyone has any experiences, PLEASE HELP.[img]/wwwthreads_images/icons/frown.gif[/img]

Robert87yj[img]/wwwthreads_images/icons/tongue.gif[/img]
<font color=blue>engine rebuild w/4.0 head done, now for the MPI</font color=blue>
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post #2 of (permalink) Old 06-12-2000, 06:12 PM
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Re: MPI DOESN\'T WORK--PLEASE HELP.

Sounds like you have taken on quite a project. Read everything you can find about the system. Get a manual on the donor car. I read for two years before I put a TPI in my Jeep and it paid off. It started first time.

At least on my TPI, the hot runs to the injectors. The computer supplies the ground. This is done to avoid blowing a circuit out on the computer should an injector wire get shorted to ground. I don't think you should have voltage to the injectors if the key is off. If it's anything like mine you should have two 12 volt feeds to the computer. One should be hot all the time, to keep the memory, and the other should be switched with the ignition. Sounds like you might have them reversed.

As to the won't start, I'd check to make sure you are not 180 out on the timing and also for vacuum leaks, big vacuum leaks like forgot to plug the hose that used to go to the...

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post #3 of (permalink) Old 06-12-2000, 06:48 PM
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Re: MPI DOESN\'T WORK--PLEASE HELP.

The mpi system is manufactured by Mopar. It even comes with obstru... I mean instructions if they could be called that. No donor engine, maybe if I had gotten the FI off of a donor engine this would be a little easier. The check engine light is supposto blink with error codes, but doesn't/ This sure is frustrating. I find duct-tape and tie-wire splices in the wires, I wonder what else was done to the jeep that I didn't find.

Since I'm an ellectrical idiot, I let my dad do the wiring, especially after finding the above mentioned duct-tape tie-wire splices in the wire loom. I'll go over the instructions again and see if there is any wire running to the wrong place. I have already gone over the vacume tubes twice. Maybe I should get a friend to double check. I can't find things right infront of my face some times. Most times when I get aggravated.

Thanks for the help so far...
Robert

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post #4 of (permalink) Old 06-12-2000, 07:36 PM
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Re: MPI DOESN\'T WORK--PLEASE HELP.

Try pulling the dist. and backing it up one tooth. The instructions for stabbing the dist. arn't very clear. When it is pinned or the dot is lined up, as you install it, the rotor will turn forward from the mesh with the cam. That puts it too far forward by one tooth. When it is installed properly, the rotor should be about 1/8 inch behind (counterclockwise) the number one button on the cap. The sysmtoms will be exactly as you describe, very hard starting if at all, and some backfiring.

Normally the injectors are powered from the A.S.D. relay, but the circuit isn't complete until the p.c.m. grounds them.

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post #5 of (permalink) Old 06-12-2000, 07:59 PM
Robert87yj
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Re: MPI DOESN\'T WORK--PLEASE HELP.

I'll go and try adjusting the distributor tomorrow. I'm too frustrated with the jeep's engine right now to work much on it. I'm thinking about going down stairs and grabbing the box of scrap steel, the welder, and some implements of destruction and making some little thing. Maybe I'll design a steel consul to go inbetween the new seats. magazine rack? I don't know. As long as I don't have to look at the engine any more tonight I;ll be happy. It is frustrating having it this close and it not running.

I really appreciate all of the help so far. I'll have to get to it tomorrow. My dad said that he would call Hesco about it tomorrow on his dime at work to ask there also. I guess it is one of the fringe benefits of working in maintenance for the US Post Office. he also has use of a full machine shop. Maybe that will come into use in the future. Now if I could just get it to run[img]/wwwthreads_images/icons/frown.gif[/img]

Thanks again...


Robert87yj[img]/wwwthreads_images/icons/tongue.gif[/img]
<font color=blue>engine rebuild w/4.0 head done, now for the MPI</font color=blue>
post #6 of (permalink) Old 06-12-2000, 08:15 PM
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Re: MPI DOESN\'T WORK--PLEASE HELP.

Just a Guess,but could the elec. fuel pump be installed backwards??? I have heard of that a few times around here.
Good Luck.....Herbie

post #7 of (permalink) Old 06-12-2000, 09:14 PM
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Re: MPI DOESN\'T WORK--PLEASE HELP.

1. I would remove an injector(leave wires hooked up) and test fire it into a container, this will let you know if the: fuel supply system is working, if the ecm is seeing engine rotation, and if the ecm is firing injectors
2. I would remove the distributor, (leave wires hooked up) spin the distributor by hand with the key in the on position, this will verify that there is good spark with out the engine start circuit supplying power to the distributor.
good luck, jjc

post #8 of (permalink) Old 06-12-2000, 10:46 PM
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Re: MPI DOESN\'T WORK--PLEASE HELP.

Seems to me you're getting excellent technical advice here, which I wouldn't pretend to be able to add to.

What I can tell you is I think you're smart to just set it aside for the evening and do something else. The worst messes I've gotten myself into, working on rigs, is pushing things to the point where my emotions start to over-ride my thinking. This usually occurs late at night after hours of careful work have not gotten the engine to start, or the switch to operate the solenoid, or the spring to fit properly on the perch or whatever.

The best mechanics I ever met were all guys with a super calm, patient disposition. I lack that valuable trait, but I did learn to compensate by putting the tools down when I got frustrated and started to get angry.

It will all still be there tomorrow.


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post #9 of (permalink) Old 06-12-2000, 11:04 PM
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Re: MPI DOESN\'T WORK--PLEASE HELP.

Spinning the dist will only fire the injectors. The spark reference on the spfi kit is determined by the crank angle sensor.

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post #10 of (permalink) Old 06-13-2000, 10:45 AM
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Re: MPI DOESN\'T WORK--PLEASE HELP.

Thanks for all of the suggestions and help so far[img]/wwwthreads_images/icons/smile.gif[/img]...

After reading all of the posts and being able to sleep on it for a night, I think that problem would be in the timing. The most frustrating part of this is that I didn't do all of the work. I let my dad do some of the work when he had the time and I didn't.

The fuel pump is on the right way because I get positive pressure at the injectors, thought that would have been an easy problem to fix. But after thinking about it after some much needed sleep I think that it might be the timing--one or two teeth off--180 off....one of those.

I'll work on it this evening. I'll be sure to let everyone know when it runs.
thanks again for all of the suggestions


Robert87yj[img]/wwwthreads_images/icons/tongue.gif[/img]
<font color=blue>engine rebuild w/4.0 head done, now for the MPI</font color=blue>
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