BT losing residual fuel pressure

[marvin]

my BT is losing residual pressure. after shutting down the engine, residual pressure drops from 40 psi to 30 psi in less than 2-3 mins ... down to 0 psi in 15-20 mins. here is what i have:

fuel pressure reg ... replaced 2 yrs ago w/ TOMS adjustable FPR.
fuel pump ... replaced 1 yr ago w/ mr2 gze fuel pump (OEM).
injectors ... cleaned 3 months ago. i was told they have been pressure tested and were fine.

after the fuel pump was replaced and the injectors were cleaned, the problem remained. i pulled the fuel return line after shutting the engine; there was no leak from the FPR but the residual pressure was still dropping.

symptom: hard starting when the engine is warm/hot.

any clues on what else can go wrong or what to look for? thanks in advance.

marvin

[sundee]

is it running the stock ecu?
every time u turn the key to the "on" positiong the ECU should Prime the fuel pump, the fuel pressure in the line will decrease once the pump stops.
is your FP gauge measuring fuel pressure before the reg? or i should just say is it setup to measure pressure inside the rail?
if its stock ECU get the manual and go through the checklist.
it sounds like your ecu is not priming the pump to me.

[Javal]

I agree with the above statement. Residual pressure should not matter much if your pump is priming every ignition cycle like it should. So check that it's happening.

If you were losing pressure due to a fuel leak, you'd smell it (even if it is a small leak) and it'd be losing pressure alot quicker than that.

[Jonny Rochester]

after shutting down the engine, residual pressure drops from 40 psi to 30 psi in less than 2-3 mins ... down to 0 psi in 15-20 mins.




Seams normal to me. What is the exact problem?

[Vezza]

is it running the stock ecu?
every time u turn the key to the "on" positiong the ECU should Prime the fuel pump, the fuel pressure in the line will decrease once the pump stops.
is your FP gauge measuring fuel pressure before the reg? or i should just say is it setup to measure pressure inside the rail?
if its stock ECU get the manual and go through the checklist.
it sounds like your ecu is not priming the pump to me.

Hey, about the ecu priming the pump when the key is on. It should prime it for about 5 secs or so right? I just noticed today that I don't hear the pump whine when I turn the key to on. But the car starts ok... maybe I didn't wire the pump properly?

[marvin]

Seams normal to me. What is the exact problem?

the annoying problem is hard starting when the engine is hot.

before i had the injectors cleaned, i thought the injectors were dirty/leaky causing the combustion chamber to be flooded with fuel before cranking. i sent the injectors out for cleaning but still had the same problem. the injector cleaning company said all injectors were pressure tested before being returned to the customers.

i was told that the loss of residual fuel pressure can be caused by leaky fuel pressure reg, fuel pump check valve, or injectors. i have new FPR, fuel pump and cleaned (and supposedly pressure tested) injectors, but still couldn't fix the problem ... :(

marvin

[marvin]

is it running the stock ecu?
every time u turn the key to the "on" positiong the ECU should Prime the fuel pump, the fuel pressure in the line will decrease once the pump stops.
is your FP gauge measuring fuel pressure before the reg? or i should just say is it setup to measure pressure inside the rail?
if its stock ECU get the manual and go through the checklist.
it sounds like your ecu is not priming the pump to me.

yes i am running a stock ecu. when i turn the key to "on" position before cranking the car, the fuel pressure gauge still reads 0 psi. the fuel pressure gauge is at the fuel filter supply line.

marvin

[Golberg]

Seams normal to me. What is the exact problem?

Yeah, the fuel system isn't meant to stay pressurised.

First thing you should do is to remove your adjustable fuel pressure regulator and put the stock one on, you have no need for an adjustable one.

Fuel pump does not prime with a factory ECU, it only switches the pump on once you turn the key to START. Well in reality the ECU doesn't turn the pump until the engine has actually started. The circuit opening relay turns the pump on when you're in the START position.

Its quite possible that some dope hasn't wired your circuit opening relay/hasn't used one at all and that only once you've cranked it for a while the ECU then triggers the pumps on and finally the car starts.

To test for this, check that your pump is getting voltage when you're in the start position. You don't even need to have the starter connected. If you disconnect the trigger lead to your starter and just turn the key to start, you should be able to hear the pump switch on.

[sundee]

^^ thats right, circuit opening relay turns the pump on! its all coming back to me.
i sware my pump turned on when the key turned to the "on" position.. mayb im a bit nutz.

just reading your 1st post again... mayb try this...

im not sure if u have a Fuel pump test connector?
if u do.. warm the car up to when ever it is most unlikly to start.. where it has its most problems.
switch the car off, bridge the test connector, this makes the pump run while the terminals are bridged, then start the car, if it still has the same issues then its not the pump.

do as golberg said and change back to the stock FPR.