Takes longer to start after AFPR install

[defiancy]

I've got a few questions/problems that maybe you kind folks can help me out with.


I just installed an AEM AFPR into my car and set it to 38 psi. Prior to that my car started up pretty much instantly when I would crank it. After the install the car now takes a good three-four seconds of cranking before it fires up and starts. Sometimes I'll crank it and let off and it'll sputter and start up. The car runs fine otherwise and according to my AEM wideband my A/F ratio is normal as well.

What could be causing this delay?


I also am getting extremely horrible gas mileage. I generally fill my tank up all the way with 12 gallons or so. That 12 gallons will get me about 200-220 MPG, compared to an old 95 GST I used to have that got at least 280-300 per tank. What could be causing this? I haven't noticed my car running super rich and the car idles and drives fine, it's just getting horrible mileage.

And finally a few boost related questions. Sometimes when I am under boost and get above 10-12 psi my car will stutter for a few moments in the middle of boosting. The A/F ratios look fine, if not a bit rich when I drive at mid-WOT throttle. Just wondering what I should check or what that stuttering could be?

Here are the mods on the car:
Full exhaust, 3' GM MAF + MAFT, Greddy RS BOV, 550cc injectors, rewired 190, intake, AFPR, MBC,

I'm still running the stock 1g side mount and a stock 14b set at 19psi. Aside from what is mentioned the car runs great and has no other problems. Thanks for your replies!

 

[Black'95]

I've heard before of some gs having issues with aftermarket AFPR's letting the fuel pressure drain off when the car is turned off. I know my AEM one does it. The delay in starting would be caused by the fuel pump having to refill/pressurize the fuel system before the injectors will squirt enough fuel to run the car. Next time before you start the car after its been sitting for a while, pop the hood first and look at your fuel pressure gauge. If you don't have a fuel pressure gauge, there's a simple fix: get one! Lol! The AEM AFPR's have the little port on em for a gauge.

And as far as the car breaking up under boost, check the plugs for the proper gapping (.028-.032), and check for boost leaks. Boost leaks cause all kinds of freaky stuff to happen.

 

[sethpatch]

I had the same with my afpr, it just doesnt bother me.

 

[iBoostDSM]

Do a BLT for the stuttering. Also since you have a AFPR, make us of it, and increase the base fuel pressure to 43.5psi, that is generally what injectors are flow tested at.

 

[rlacasse1]

And did you set the base fuel pressure correctly?

 

[TSiAWD666]

After installing my afpr I experienced the same symptoms and continue to do so. It's annoying to crank a few extra seconds. Doesn't seem to affect anything else as I seem to be able to tune fuel generally ok. I'm not data logging my fuel pressure nor can I view it while driving so take my "it's not a problem" experience for what it's worth.

The only possible fix I ever came across was found by an Evo owner, and at the moment I forget the name of the thread but it was over on evolutionm.net. His fix was for a ball/spring type AFPR where the ball seat was not cut well in the aluminum and not sealing well against the ball, allowing the pressure to bleed off almost immediately after shut off (and other issues I think, like fuel pressure not following boost at higher pressures accurately, but I forget). He used a special cutting tool (I forget the name of the type of tool too ) to create an angled seat for the ball instead of the original 90-degree angle, and this solved his problems.

I've been meaning to try this on my afpr but I haven't gotten around to taking it to my local machinist.

 

[gieri002]

^ Thank you, that is some great info!

 

[IrishBeatdown]

EDIT: replied to another thread on this thread by accident

 

[PrimerPLus]

I have this issue too. When I was installing my aeromotive AFPR I watched a youtube video made by one of the members on this site. He was installing a Fuel Lab AFPR and he said that after his install he noticed it took longer to start the car. More seconds of cranking. So I just thought that was normal. But it is annoying. Makes people think that your car isn't going to start up .

From what I understand you can't even just turn the key forward to let the fuel pump prime the system before you start it up either. I also read some people use some kind of check valve to keep the pressure in the line but I also heard that will cause poor gas mileage.