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post #1 of (permalink) Old 07-27-2003, 08:21 PM Thread Starter
 
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MPI fuel pump, no juice

Today I tired to hookup my aftermarket tach. After I hooked up my tach I went to bang it over and it fired up for a few seconds then died. I tried again and their was nothing. I turned my key to the on position and listened for the fuel pump and it was not pumping? What gives?? I hooked my new tach up according to the instructions in the MPI manual. The red wire on the tach to the 12V powers source, the green wire off the tach to the wire marked tach on the new wiring harness, the black wire was hooked to the ground and then I fired it up. I unhooked the tach and it still does not work. Is there a fuse for the fuel pump?? HELP!!!!

Nate..
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post #2 of (permalink) Old 07-27-2003, 10:05 PM
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Re: MPI fuel pump, no juice

No separate fuse. Check your connections at the pump. Throw a voltage tester at it and see what it reads, make sure you are getting juice to the pump...I've heard several people complain about premature death of these pumps...could be yours died an early death.
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post #3 of (permalink) Old 07-27-2003, 10:25 PM Thread Starter
 
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Re: MPI fuel pump, no juice

I put a meter on the fuel pump and there in no power getting to the pump. I am stumped. I don't think adding a tach to the system should short things out or cause the fuel pump to stop working. I hooked the tach to the light bluish-grayish wire that comes out of the new loom. Is this correct??

Nate
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post #4 of (permalink) Old 07-28-2003, 03:39 AM
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Re: MPI fuel pump, no juice

<font color="red">-----------------------------------NOTICE-----------------------------------
This is a SWAG (Scientific Wild A$$ Guess)
</font color>

I ran into a similar problem once with my TPI system once. It would appear that the pump only runs for a second when the key is turned to the on position and then won't run again until it gets feedback that the engine is running. I've disassembled and been commenting the code for my ECM but haven't gotten to that part yet so I'm not sure exactly what it does.

I'd guess that in connecting the tach you somehow interrupted the feedback to the 'puter. You should be able to connect a jumper to the fuel pump to force it to run then start testing. Some systems have a place to jumper power to the pump at the ALDL connector.

Did the tach work when the engine ran or did you have time to check it? Try disconnecting the tach and see if it runs without it. If it does, you know where the problem is.
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post #5 of (permalink) Old 07-28-2003, 08:24 AM Thread Starter
 
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Re: MPI fuel pump, no juice

I did remove the tach and try to start it and still no go. When I wired it up initally the tach did jump when I tried to start it. After that nothing worked. As far as jumping the connection do I just run a hot wire off the battery, or??? Do you think I caused some damage to the computer. I just followed the manual. Damn what a pain in the ass. Thanks guys.


Nate..
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post #6 of (permalink) Old 07-28-2003, 08:31 AM
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Re: MPI fuel pump, no juice

Nate, remember that the pump only runs when the computer thinks it is needing fuel...if you turn the key from off to on the pump will only prime the system then cut off. you may need to disconnect the fuel line and allow it to pump into a container to keep the computer thinking it's needing more fuel.
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post #7 of (permalink) Old 07-29-2003, 02:15 AM Thread Starter
 
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Re: MPI fuel pump, no juice

Well through the process of elimination I believe that my problem might be one of the relays on the firewall. I know one has to control the fuel system. What do you think?

Nate
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post #8 of (permalink) Old 07-29-2003, 04:49 AM
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Re: MPI fuel pump, no juice

If you haven't done so, check all fuses and replace as necesary. I would suggest unkooking the tach, and trying to run the engine without it. Sounds like you hooked it up OK, the only connection I would possibly suspect is your tach wire. If it runs without the tach hooked up, next time you wire it run the signal wire for the tach directly to the negative side of the coil. [img]images/graemlins/grin.gif[/img]
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post #9 of (permalink) Old 07-29-2003, 09:35 PM Thread Starter
 
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Re: MPI fuel pump, no juice

The first thing I did was remove the Tach from the system and still had starting problems. I checked all fuses and the only thing I believe it could be is the relay or relays. I am lucky that my jeep is not my daily driver but it still pains me to know my baby is down. Keep the ideas flowing guys.

Nate
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post #10 of (permalink) Old 07-30-2003, 06:28 AM
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Re: MPI fuel pump, no juice

Nathan, have you called Hesco yet? they are pretty good about follow up ?'s on the system. They may have the secret answer.

Hesco
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