poor idle after warm restart

[buldozr]

when i shut the car off fuel pressure isnt lost slowly, its within a second to 0psi.

theres your problem
what pump is it, did the problem start once swapped to new pump? start there, possible injector leaking or reg not holding pressure but unlikely.

EDIT: if its a china walbro, they have no 'valve' inside to hold pressure when pump is off.

 

[grimreaper]

got it from mvp motorsports, other then that i wouldnt know how to tell if it was fake, had the walbro W on it too.

it did this with the oem pump too.

 

[Nick M]

You can bleed down through the check valve on the pump, the regulator, or the injectors. Provided it isn't leaking externaly, you are leaking from one of the other places. Provided your test was legitimate.

 

[Nick M]

got it from mvp motorsports, other then that i wouldnt know how to tell if it was fake, had the walbro W on it too.

it did this with the oem pump too.

You had a rough idle when restarted warm with the OEM pump? The FPU is only for a moment, to get it running.

 

[buldozr]

rough idle could be a cyl filling with fuel while an injector sticking, double wammy, fuel rail not holding pressure and a cylinder filling up with fuel.... would want to get your injectors tested/flowed. Just my opinion, I may be wrong.

 

[grimreaper]

Yes, yes it did. I didnt pay much attention to it then, i thought that was just how the car acted.

is there a certain temp the VSV has to see before it operates?

Ill pull them off and check. Would i get a smoke show on start up with that much fuel?
idle is actually lean (15.5-16.5). When it idles rough its off the charts lean as well (along with lean missfires). only area of rich af ratios is wot.

nick m. : same issue with the vsv hooked back up and then with fpr to atmosphere, still idles like shit, Its not near as rough as it was though.

 

[nosman4]

Fuel pressure bleeding off wouldn't affect it at idle, only when starting. My car does the same thing on warm start, idles off the charts lean at about 17.5-18.0. I would start checking items such as the ECT sensor or the IAT sensor, sensors that the car looks at until the O2 sensor is warmed up. I havn't really looked into mine yet, but I will.

 

[jdub]

is there a certain temp the VSV has to see before it operates?

Coolant temp at 100 deg C.

With the VSV not connected to vac, you basically had the FP up at all times.

You do need to figure out why it's not holding FP to TSRM spec

What's stumping me is the lean condition when it does this. That's why I was leaning toward the AIT or HAC sensor....the O2 deserves a check while it's doing this too.

 

[grimreaper]

agreed, ill pull the rail off this weekend and see if the injectors are leaking.

how do i test the hac on an 89+?

 

[johnathan1]

My Supra just started doing this...it did it intermittently a few times, now it's just about every time.

I remember my Porsche 924 would behave exactly the same way due to vapor lock (infamously leaky Bosch mechanical injection system).

 

[jetjock]

You're not listening Grim....

Johnathan: The K Jet is a reliable injection system if one understands and maintains it. I'll admit it can suffer serious vapor and warm start problems if rest pressure is lost through say, a failed accumulator though. Due to the pressures involved it's also a fire waiting to happen. Other than that, German engineering at it's finest

 

[johnathan1]

I replaced every part of the fuel system but the distributor, and hot starts were still murder. It really wasn't a great car, and I've moved on...to MB 560SEC, also with Bosch mech injection. -_- Luckily it seems like this version is much better, and also uses Lambda feedback.

 

[grimreaper]

no luck with jumping the fp before restart (let it prime for a good 20-30 seconds), still rough and af ratio climbs off the chart lean within a few seconds.
Fuel pressure jumped to 30-32 psi once started (no real cranking time needed, starts right up) and dipped back to 25psi. After i primed it it jumped to the same 30-32 psi and dipped down a bit lower to 24psi but no jumping around or spikes if that helps. (base set at 32psi)

What's stumping me is the lean condition when it does this. That's why I was leaning toward the AIT or HAC sensor....the O2 deserves a check while it's doing this too.

] ran out of time tonight, ill get what the o2 is reading in the am, and the AIT sensor ohmed out perfectly in line with the temp.

 

[CyFi6]

What does running the fuel pump before starting up do? Wont the vapor, if there, just stay there, don't you need to apply vacuum to the regulator so it opens up and purges the vapor? Just not sure if i am missing something.

 

[jetjock]

Look at the TRSM procedure for checking fuel pressure. If you jumper the pump (engine off) what does pressure go to? Does it go to a value that indicates the pump is in relief? A pressure that indicates the pump is being dead headed? No, it doesn't. Where do you think pressure is being relieved?

The spring in the regulator is calibrated to maintain fuel pressure (without a vacuum bias) at 33-40 psi. The GTE uses Toyota's Type A injection system. The spec for that is 36 psi across the injectors. Note that value falls midway between the 33-40 psi speced in the TRSM for a regulator check. The regulator isn't closed when the engine is off and the fuel pump is on. Under those conditions it's doing exactly what it was designed to do: regulate fuel pressure at 36 psi. Of course, it does that by bleeding fuel (and vapor if present) back to the tank...

 

[grimreaper]

update: double checked a few things before i began to pull the injectors, i must have pinched the fuel feed line. They run side by side until under the intake mani on my setup. Pinching the return line pegs the fuel gauge at 90psi. time for a rebuild.

 

[CyFi6]

Look at the TRSM procedure for checking fuel pressure. If you jumper the pump (engine off) what does pressure go to? Does it go to a value that indicates the pump is in relief? A pressure that indicates the pump is being dead headed? No, it doesn't. Where do you think pressure is being relieved?

The spring in the regulator is calibrated to maintain fuel pressure (without a vacuum bias) at 33-40 psi. The GTE uses Toyota's Type A injection system. The spec for that is 36 psi across the injectors. Note that value falls midway between the 33-40 psi speced in the TRSM for a regulator check. The regulator isn't closed when the engine is off and the fuel pump is on. Under those conditions it's doing exactly what it was designed to do: regulate fuel pressure at 36 psi. Of course, it does that by bleeding fuel (and vapor if present) back to the tank...

Ah, so once it gets down to around 21PSI the regulator closes off to hold pressure?

 

[grimreaper]

aero. fpr is perfect inside, no rips, tears or anything. Clamped the return line closed and it held 31 psi for 5 minutes perfectly. unless im missing something, this regualtor doesnt hold rest pressure. aeromotive techs wont be back till monday and ill see what they say.

be back with o2 results when it idles rough..

 

[nosman4]

My question is why is everyone chasing fuel pressure when it has already been shown to be good? FP falling off should only extend crank time and maybe make it hard to start. The pump is making good pressure when it's running. My car does the exact same thing as grim's car and it does it until the O2 is up to operating temps and it goes into closed loop mode. It has to be a sensor that the ecu looks at for fuel estimation until the O2 is ready to give a reading. I don't think FP has anything to do with your problem. Correct me if I'm wrong.

 

[3p141592654]

I suppose the thinking is that the fuel pressure is low during this rough idle, although that is not confirmed by anything I read above.

That said I don't understand the following post. The fuel pressure should be constant under steady state conditions like idle. What is all this jumping around from 32 to 25 psi? Maybe I just don't understand what he is saying or doing!

Fuel pressure jumped to 30-32 psi once started (no real cranking time needed, starts right up) and dipped back to 25psi. After i primed it it jumped to the same 30-32 psi and dipped down a bit lower to 24psi but no jumping around or spikes if that helps. (base set at 32psi)