Anyone with a service manual: Is there a bench test for a fuel pump ECU?

[chin]

First off I want to say hello and thank you. This forums helped me to track down a intermittent connection at the fuse box, that was preventing ignition to reach my ECU. That is now resolved but...

I can get the car to run perfectly by bypassing the fuel pump ecu. I picked up 2 junkyard fuel pump ecu's the other day and neither one of them work. I just want to be absolutely certain the fuel pump ecu is/isn't the problem. With no bypass and the fuel pump ecu plugged in normally, car will just crank and no start. I can supply power directly to the fuel pump at the diagnostic connector or at the fuel pump ecu and hear the fuel pump run and car will start fine. Power is going into the fuel pump ecu via the heavier gauge black w/ red stripe, but no power leaving the fuel pump ecu from the heavier gauge green wire. Am I over thinking this? What's the chances of getting 2 bad fuel pump ecu's?

Would a crank or cam sensor prevent the fuel pump ecu from energizing the fuel pump? Thank you.

 

[sideshow]

It can be yr ecu or wiring from ecu to fuel pump ecu
But I've never seen that
Most of the time it's fuel pump ecu
U need to test with oscilloscope
Two wires from ecu to fuel pump ecu
D1 and fpr
Or try the fuel pump ecu in a perfectly running car

 

[gloverman]

What about the Drop test?

Heres how it works - take fuel pump ecu out throw into the air and allow to drop onto the concrete. Refit to vehicle

If it now starts working then the part is faulty and replace it
If it still doesnt work then its stuffed end needs to be replaced.

This test work well on most suspect components.

Pretty much as sideshow said. Best to swap it out with another know one. I have them laying around , every car I wreck I pull hem out and never use them on conversions.

Cheers

 

[chin]

What about the Drop test?

Heres how it works - take fuel pump ecu out throw into the air and allow to drop onto the concrete. Refit to vehicle

If it now starts working then the part is faulty and replace it
If it still doesnt work then its stuffed end needs to be replaced.

This test work well on most suspect components.

Pretty much as sideshow said. Best to swap it out with another know one. I have them laying around , every car I wreck I pull hem out and never use them on conversions.

Cheers

Well... Please mail all fuel pump ECU's to me in Atlanta, GA (USA). They are needed. Sideshow, thank you for the assistance. I have 4 fuel pump ECU's (all from junkyard). What's the possibility of all 4 of them being bad. Car runs fine if I bypass the fuel pump ecu, cranks but no start if I do not bypass it. I have to do a search and see if there is a test to determine if my main ecu is good is my next logical step. I tested cam and crank sensors. They seem fine... My car is a 1994 LS400 and it can't pass emissions here in the states for some reason, nox are high as well as hco? I don't think bypassing the fuel pump ecu would do that? I also cleaned my egr valve and ports the other day which had some build up.

 

[sideshow]

The fuel pump ecu also controls speed of pump
So it might just make the emissions slightly out if bypassed
Does it fail by alot

 

[chin]

It was failing by a mile the first attempt. The numbers got a little better on the second attempt when I cleaned out the EGR, but my numbers are a little less than double the allowable limits. I just find it hard to believe that I have 4 bad fuel pump ecu's, but stranger things have happened. Now I need a complete stranger willing for me to take their car apart and borrow their fuel pump ecu (that shouldn't be too hard). I don't have access to an o-scope...

 

[Zuffen]

Your description of how it's failing Smog suggest you have faulty cat converters.

I'd be inclind to by-pass the Fuel ECU and get it tested pre cats to see how it is there.

I would think some junkyard cats wouldn't cost much and may just solve your problem.

4 junkyards Fuel ECU's being faulty is a remote possibility.