hey guys, i have a 1988 iroc-z with the L98 ive been looking at some threads on here about hard starting tpi's and i saw a couple things associated with my same problems. im thinking about replacing my fuel pressure regulator with an ajustable one from T.P.I.S for 90$ any coments or suggestions? also what are the pressures on my motor for both running and priming? thanks guys.

 

bbk regulator from summit 65.00

 

first comment was right, dont buy it from tpis, they are overpriced and like to rob people. buy it out of a summit magazine for a reasonable price.

 

I have been researching this topic in relation to my porting the plenum project. Here are a few thoughts. First, search this TPI site by the key words "Adjustable Fuel Pressure Regulator". Some people have comments that the adjusting srew is too long for the stock set up. I am considering the Holley AFPR because some one said they did not have trouble with the screw problem and mainly because of the name Holley has in fuel systems. I have a 5.0 litre TPI. The Holley part number is 512-501. Price at Jegs $82.88US or Summit Racing $82.99US or $82.45Can at a store in my hometown. Second, read the frequently asked questions on this TPI message board. Third, read about AFPR in FAQ under the Tech Central heading on this site's home page. Fourth, I do not know what you have done to your car; however, if you do this project now is the time to consider porting the plenum and runners and maybe look at better fuel injectors. Fifth, you will need some gaskets for this project, especially if you remove the plenum and runners, try Fel Pro a set's part number is MS93160 for $15.39US at Summit Racing.

 

the bbk one i had to go to a hardware store a get a shorter screw because was hitting the bottom of the intake,i had the holley one but it is hard to adjust the screw sometimes and it stop holding pressure.ps it comes with new gaskets.

 

check out the aeromotive fpr's from summit or jegs.

 

Make your own, works perfect:

www.gmtips.com/3rd-degree/dox/tips/afpr/afpr.htm

 

hey tank you guys you have been a lot of help i will probably go with the holley just because i havent heard anything bad about them. but i did have just one more question. what is everyones problem with tpis? everyone ive tsalked to doesnt like them?

 

Maybe I'm missing something here, but, installing an afpr will not necessarily solve your hard starting problem. Is gas leaking into the plenum? I would first look at the fuel pump relay, and the cold start injector.

 

actually i havent torn it apart yet im just trying to find the problem before i take it all apart but im sure i will anayway i have nothing else to do while my car sits in the garage durring winter. i havent checked for leaks yet. im just trying to find people with the same problem ( which i did) and getting info from them. i am obviously going to check the regulator for pressure before i replace it. but i havent checked the relay and why would i? it alsways kicks on at the turn of the key? or is there more too it?

 

Dont let the screw thing stop you. Crane has a reasonably priced AFPR, you can just cut the screw down to size, to clear the bottom of the plenum. As for TPIS, just look at the price of their cams $379.00, the last time I looked. You can have Comp Cams custom grind you one for half the cost. Two things Tpis does well, is advertise, and take your money....

 

The fuel pump relay does not stop after it primes the rails, it is constantly energised when the engine is running. If the relay is weak or jittery it may or may not cause fuel delivery problems.

 

well i knew that much but, a relay is either an on or off devise the only way to send a different voltage is if the contacts are corroded but i still dont think that would be the problem but hey sometimes wierd things happen thanks again guys!

 

i had the same problem hard starts, try pulling the vacum line to see if it smells like fuel. If you see or smell fuel it probably is shot. I replaced mine with the holley afpr and it works great. also added a autometer guage mounted directly on the fuel rail so i can adjust it

 

This sounds like my problem I just recently started having in the last week in a half. I have to crank the car at least 3 times before it will finally turn over. After its warmed up, its easier to start it. Another reason I think its fuel related is that at certain times when I'm driving, usually when I have my foot in it, it will seem like the car will just die for a split second, then come to life again. It will throw you forward a little in your seat, its so abbrupt. I think either my fuel pump is going bad (even though it was replaced about a year and a half ago) or that it could be the fuel pressure regulator crapping out on me. The situation with the car dying for split seconds has only happened 3 times, all within the last 48 hours.

 

I dont know about your start problem, but I installed a Holley AFPR, replacing my Crane unit. The Holley is very easy to adjust. It has a large serated wheel on top for easy adjustment. No tools required.

 

Doc: What Holley AFPR did you use? I am considering a Holley AFPR for my 5.0 liter TPI engine. I was considering the 512-501, which is a kit that modifies the OEM fuel pressure regulator. Then I saw their 512-504-5, which looks to be seperate unit.

 

It must have been the 512-501, I saw a picture of the 504, so I know its not the 504.

The 512-501 is listed on Holley web site to be for '85 to '92 TPI Camaros & Firebirds.

 

holley #512-501

 

Yep, thats the one.

 

I just recently put an afpr on my TPI because i got bigger injectors and was wondering how you go about setting the pressure. Also got a gauge on there too. Do you leave the vaccum line on or off when adjusting? I noticed it was putting too much fuel in and blowing it out the exhaust.

 

You disconnect the vacuum line from the back side of the plenum that runs to the AFPR while the engine is idleing and plug both open ends. Read the fuel pressure.

If you changed the fuel injectors you should have gotten a custom chip burned with the new flow rate of your new injectors.

Otherwise you will have to lower the fuel pressue way down to get back close to the old fuel flow rate, which defeats your purpose of new injectors. I am assuming the new injectors are of a higher flow rate.

 

501 is the model I use on my 88' IROC-Z.

Did some hacking while changing it out. Can't call it a mod, don't want to start a riot.

 

you guy`s will see that the holley fpr will stop holding pressure will start to bleed fuel pressure down,the wavelock design spring no good remember antoine told you,maybe mine was bad.

 

yeah i have that same throttle responce thing going on too. where if you stab the throttle it will practically die and then come alive and pin you in the seat. im sure i will be replacing it with the holley ajustable next week. thanks guys for all your input very helpful!