EFI fuse blowing on acceleration.

[suprabones]

Hello everyone,

Before anyone gets there undies in a bunch.. I have used the Search function very extensivly for a week now. Now its time to ask some Q's.

Car will hold a idle for a hour+ no problems. I put the sucker in drive and give it gas.. sometimes I can drive for maybe a few feet, sometimes I can go for a whole block. The EFI fuse blows..

I have checked the EFI circuit for shorts.. I have used the multimeter on: EFI Relay, COR, Fuel pump. The EFI relay is to hot to touch but gives me a good reading on continuity. checked resistances for O2 sensor wires from ECU to sensor and all is good. All seem to be in working order. Fuel pump is coming on with a jump from +B to FP.

The only mod that I am running that is tapped in to the +B on the ECU is a old school 5 knob AFC.. All wiring looking very good.

Could the Fuel pump be drawing to much amps under load?? How could I test for this? What else could possibly be blowing the fuse only when I give it gas in drive??

Any help would be a great help.. This is my daily driver.

-Matt.

 

[Another MkIII]

A component can have good continuity and be bad. The problem, just might not show up until you put current to it. So don't go eliminating the EFI relay as your cause just yet.
-AM3

 

[suprabones]

A component can have good continuity and be bad. The problem, just might not show up until you put current to it. So don't go eliminating the EFI relay as your cause just yet.
-AM3

So you thinking its a possibility that the EFI main relay could be bad? I have never tryed touching it when my car ran fine.. but today that sucker was to hot to even pull out of the relay socket.

-Matt.

 

[Another MkIII]

So you thinking its a possibility that the EFI main relay could be bad? I have never tryed touching it when my car ran fine.. but today that sucker was to hot to even pull out of the relay socket.

-Matt.

I'm not saying it is your problem for sure, I'm just saying that just because it has continuity doesn't mean its good.
-AM3

 

[Poodles]

EFI relay runs very hot, so that's normal. Outside of that, when did this start happening? What did you do last?

 

[suprabones]

EFI relay runs very hot, so that's normal. Outside of that, when did this start happening? What did you do last?

Just happened last week, Friday. Was at a stop light waiting to turn.. everything was running fine.. went to give it gas and it blew the fuse.. I am running an auto tranny.

Its strange, I can keep it in park or neutral and rev it up to redline just fine, but put it in drive and try and go... thats another story.

I have not done any work on the car other than do the normal oil changes.

I dont have any VSV's, EGR circuit, no fuel up VSV, so that side of the EFI circuit has no shorts in it.. I cut the plugs and heat shrinked the wires so they cant get corroded.

Maybe I need to take out the AFC and re-vert the wiring to stock at the ECU and see if its the AFC fried?

-Matt.

 

[Another MkIII]

Just happened last week, Friday. Was at a stop light waiting to turn.. everything was running fine.. went to give it gas and it blew the fuse.. I am running an auto tranny.

Its strange, I can keep it in park or neutral and rev it up to redline just fine, but put it in drive and try and go... thats another story.

I have not done any work on the car other than do the normal oil changes.

I dont have any VSV's, EGR circuit, no fuel up VSV, so that side of the EFI circuit has no shorts in it.. I cut the plugs and heat shrinked the wires so they cant get corroded.

Maybe I need to take out the AFC and re-vert the wiring to stock at the ECU and see if its the AFC fried?

-Matt.

What about in reverse?
-AM3

 

[jetjock]

^ And I thought post #2 was strange...

OP: Often caused by shorted O2 sensor wiring or a short to ground in the harness where it chafes on the rear of the intake manifold...

 

[suprabones]

^ And I thought post #2 was strange...

OP: Often caused by shorted O2 sensor wiring or a short to ground in the harness where it chafes on the rear of the intake manifold...

I am sick of this old wire harness!! I have had nothing but troubles with it the whole time I have had the car. Car still does not run...

-Matt.

 

[crisp]

Along the lines of jetjock... although your remark that you have no EGR CIRCUIT makes me wonder... do you mean NO EGR PLUMBING? Left-side EGR pipe passes UNDER the main harness... if that CLIP that holds the harness fails or has become disconnected... the harness can "settle" down near or onto the EGR's hot pipe. ESPECIALLY on acceleration, when the motor "torques" and the lift up causes contact. The hot EGR pipe can "melt" through the main harness (it's on the UNDERSIDE, so you have to FEEL for the spot!) and cause the short!


I fought that issue for FIVE YEARS of car down-time... then on my FIRST DAY in Supramania, someone suggested it based on my symptoms. VIOLA!


G/L with YOUR solution!



EDIT! Found my original post on this! My VERY SECOND POST in SM!



http://www.supramania.com/forums/showthread.php?t=45553


-crisp

 

[suprabones]

Sorry for the late post back, Problem solved.. I removed the whole harness to find this issue.. Seems that the +b wire from the ECU passing through the firewall was cracking due to age.. cut the old wire out and re-ran a new line.. runs perfect... Although I have a new problem lol.. that is for another day.
Thanks everyone!

-Matt.

 

[Dirgle]

Thanks for getting back to us on the solution, few people do that anymore. It helps others, and perpetuates the usefulness of this wonderful site.

 

[crisp]

Thanks for getting back to us on the solution, few people do that anymore. It helps others, and perpetuates the usefulness of this wonderful site.

DITTO!




Nice closure.


-crisp