Wont Start

[grantypanties218]

i have been lurking and researching here for about two weeks now have learned a lot already

anyways i bought a 95 q45 about 3 weeks ago for 800. the guy said he was driving stopped at a stop sign and it shut off he said it had stalled before but would fire right back up. the guy also mentioned he had a mechanic look at it and said it was a fuel pump so i trailered it home and immediately started researching, i tried holding the gas pedal down for up to 2 mins while trying to crank it over with no success so i just ordered a fuel pump from IOS my only concern that the FPCU might also be bad i have read that there is a way to bypass it to see if the FPCU is bad i have also read that there is a way to fix a bad FPCU

i have tried to search but i came with up with nothing can someone give me a link to the diagnosis and fix for the FPCU

thank you
grant

[Infinitiguy19]

Your in luck:

Here is what I did today:
Connected voltmeter to measure amps between fuel pump fuse terminals and these are the results (engine warmed up):
1. Switch on (before cranking) - 2.8 amps for ten seconds, then drop to zero.
2. When cranking - 4.5 to 4.8 amps.
3. On idle (in park or neutral) - 1.96 /+- 0.01 amps (feel minor vibration but not too bad).
4. When standing still (in drive) - 2.05 /+- 0.01 amps (feels very smooth).
5. Cruise without load - 2.3 /+- 0.01 amps.
6. Full throttle - 3.5 /+- 0.01 amps.

The interesting thing is that after accelerating whenever I leave the pedal the amps drop to 1.92 and one time it even dropped to 1.89 amps (noticable vibration)! When I completely stop the amps raise to 2.05 and everything feels normal. When driving, if I don't touch the pedal the amps drop to 1.92 and feel a minor vibration. From other posts it seems that 1.92 amps is too low and you said that it should not drop below 2.3.

My question - is this the fpcu?? I replaced the fuel pump about a year and a half ago (it was humming like a cow) but didn't touch the fpcu.

Areznik

The FPCU seems to be working fine [from the amperes you provided] still doesn't mean the pump is providing the correct pressure/volume.

Full throttle at what rpm [3.5 amps] all the way to redline?

What is accurate hot idle rpm in park and in drive rpm........inside tach not accurate enough to answer this question!
What is IAC percentage at idle in park, % with AC turned on?

Again what is fuel pressure? One you measure the WOT pressure we can affirm the pump is ok.........not till then!

Q45Tech

throttle-position-sensor-question-t6502 ... %20balance

Your measurements should be the same as above.

[goody90q45]

To bypass the FPCU unplug the connector and run a jumper from the pin shown in the pic to ground.