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Please Help!! MPI Relay or ...?

Gmoney1983

Well-known member
Joined
Oct 13, 2012
Messages
91
Location
SLC, UT
So went to got borrow a few tools from a friend. Getting on the highway on the way home and go to give it some gas after shifting into3rd gear. Car falls flat on its face. Look down and notice the tach sitting at zero rpm. Great I'm thinking i just ran out of gas, no big deal gas station at the nest exit. Walk up there and get some fuel and put it in the car. Crank, no start. Repeat. Drain battery trying to start the car. Call roadside assistance and wait forever. guy brings me some more fuel and a battery jumper box. Put the rest of the fuel in the car and hook up the jumper box. Crank, no start.
So i decided to check the main fuse box under the hood and noticed that the mpi realy circuit breaker had popped. Grab the breaker from the cooling fan. crank, no start, poppped another circuit breaker.
At this point it's too cold to screw around anymore so I called my friend and got a ride back to the house. Going in the a.m. to meet a tow driver and get the car home.
So my question is, would the mpi relay being bad take out the circuit breaker repeatedly? Wiring problem? I've already fixed several of the previous owners "repairs". Also what can cause the mpi relay to go out? Or to cause the breaker to pop? Car seems to be fine other than this and was running well up until the breaker popped.
Thanks all.
 

toybreaker

iconoclast
Joined
Apr 30, 2006
Messages
3,581
... possibilities are almost endless at this point.


I would suggest you look at the fuel pump wiring in the trunk area to see if anything has been tampered with/"improved".

Unplugging the mpi relay and firing in another fuse will tell you if it's on the key side or mpi side of that circuit.

Other places to look are the 02 sensor harness (heater wires), the injector resistor pack up on the firewall, and ignition areas of life.


Send me a pm with your phone number and I can walk you thru a few other things/tests.



I'm travelling a lot right now, but I *might* be able to do a drive by later this week while we have this nice weather.
 

Gmoney1983

Well-known member
Joined
Oct 13, 2012
Messages
91
Location
SLC, UT
I will start in the trunk area. The car does have a walbro 255 installed, so I guess i will see how well. calling the roadsise people to get the car right now.

Thanks for the offer. I will definitly be pming you here in a bit.
 

Gmoney1983

Well-known member
Joined
Oct 13, 2012
Messages
91
Location
SLC, UT
Alrighty. Finally got the car home.. Started checking stuff out in the trunk area. No broken wires or anything that i could find. Everything actually looks good back there. I did not remove the pump/sender assembly to check inside yet. Pulled the mpi relay off and it looks good, no corroded pins or anything on the connector or relay. And all the wiring is intact. Except for the wire in the pic bleow. Im assuming this was a wire for a/c maybe? if you could check it out and let me know what you think it is. With the relay pulled I went to put on the jumper cables after attempting to start the car. Barely had enough juice to turn over, Started hooking up the Positive batt cable and realized it was very loose. Grabbed a wrench to tighten and what happened is what you see below in the pic. Snapped clean off with very minimal turning effort.
So I'm gonna go ahead and start there. headed to advanced now to grab a terminal. Going to install it and put everything back together and start from there. Really hoping its that easy!!


 

Gmoney1983

Well-known member
Joined
Oct 13, 2012
Messages
91
Location
SLC, UT
ok, a little more testing done. Pulled the fuel pump assembly out. No damaged wires in ther. everything looks good. Pulled the mpi relay out and cranked the car.No blown fuse. Mpi relay hooked up, blown fuse. All wiring looks ok. Gonna bust out the multimeter and do some testing when i get back from running a few errands.
Where should i start? What else should i look at?
 

ktmrider

Well-known member
Joined
Sep 10, 2007
Messages
3,128
Location
Tempe, AZ
Quoting toybreaker:
... possibilities are almost endless at this point.

Other places to look are the 02 sensor harness (heater wires)

Another good call there TB... /ubbthreads/images/graemlins/applause.gif
 

Gmoney1983

Well-known member
Joined
Oct 13, 2012
Messages
91
Location
SLC, UT
got her all wired back up. couldnt find a new o2 connector, so I just picked up a four way trailer connector. Hoping it works out. warming up a little, then go reinstall fuel pump and retest.
 

Gmoney1983

Well-known member
Joined
Oct 13, 2012
Messages
91
Location
SLC, UT
Woohoo. She runs!!! Huge thanks to toybreaker, I never would've thought to check the o2 wiring had you not mentioned it. That was my problem. Also huge thanks for be so willing to help out.
 

Gmoney1983

Well-known member
Joined
Oct 13, 2012
Messages
91
Location
SLC, UT
Same thing again after about 25 miles of driving. Tomorrow morning I think I'm going to try and do a fuel pump rewire. Do you guys think this may help? Kinda at a loss here. All wiring is good. I think I may just be frustrated at it for the night. we will see what tomorrow brings.
 

Gmoney1983

Well-known member
Joined
Oct 13, 2012
Messages
91
Location
SLC, UT
Got it all figured out finally. Note to self: always check both sides of the connector if you are going to repair your wiring. 700 plus miles and all is well. thanks for the help everyone!
 
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