Fuel Pressure w/vacuum - the same
 

The fuel pressure remains the same whether vacuum is applied or not,, and the lowest I can set it is 40 pounds (it has the stock pump). You can increase the pressure,,, and it still makes no difference,,, stays the same with or w/o vacuum. Has anyone had this type problem?

Thought it might be the AFPR,,, and I swapped the Crane with an Accel (didn't know they were practically the same). However, it made no difference. I also made sure the AFPR vacuum port was not leaking.

Any ideas?

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86 IROC - 9.8:1 - 355, TFS twisted wedge heads, 218/228-110, fully ported GM base, SLP runners, fully ported plenum, 52mm BBK, 1 5/8" headers, single 3" Dyno-max, Jet Custom "chip", B&M Megashifter, 245/45ZR17s on Budnik Mercury 5s (ok they're 212 Eagles)

Hi BadSS since no one else seems to want to take a stap at it,,, looks like you'll need to check the regulator base for some type of restriction,, or possibly a restriction in the return line. No telling what is wrong with it,, since you are the third owner. But,,, if that's not it, and since you refuse to spend anymore "serious" money on the EFI,,,, you can always pull off the TPI system you spent 20 plus hours on porting and hundreds of dollars on,, and put that POS 750 Holley, mechanical fuel pump, and RPM intake you have in the garage. Dang this sucks!!!!

Well,, it was the regulator,,, took the old one apart,, everything looked fine. I took a gamble and replaced the old one with a new GM unit ($95),, and it's working correctly. Go figure.

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86 IROC - 9.8:1 - 355, TFS twisted wedge heads, 218/228-110, fully ported GM base, SLP runners, fully ported plenum, 52mm BBK, 24# FMS, 1 5/8" headers, single 3" Dyno-max, Jet Custom "chip", B&M Megashifter, 245/45ZR17s on Budnik Mercury 5s (ok they're 212 Eagles)

Bad what are your readings with a stock regulator at idle with vac hose on and vac hose removed?

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87GTA,350,Auto,MAF screens removed,K&N,modified air intake,ADSchip,3:73s,3inch cat back Flowmaster,TPS.54,Bosch Plat plugs,base timing 6BTDC,Bilstiens in the rear....,don't let yer meat loaf

RP,,, at idle no vacuum it's 42#,, with the vacuum it drops to right at 35#. Since I know the replacement regulator is OK,, I'm going to try the AFPR,,, using the stock regulator's diapram.

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86 IROC - 9.8:1 - 355, TFS twisted wedge heads, 218/228-110, fully ported GM base, SLP runners, fully ported plenum, 52mm BBK, 24# FMS, 1 5/8" headers, single 3" Dyno-max, Jet Custom "chip", B&M Megashifter, 245/45ZR17s on Budnik Mercury 5s (ok they're 212 Eagles)

bad my reg looks stock ....but it gives me 37 at idle with vac and 47 with the vac hose removed and the performce is very good.Even though the reg looks stock...its possible someone messed with it.All the other STOCK tpi's i've worked on were 39psi vac hose on ....44 vac hose off.

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87GTA,350,Auto,MAF screens removed,K&N,modified air intake,ADSchip,3:73s,3inch cat back Flowmaster,TPS.54,Bosch Plat plugs,base timing 6BTDC,Bilstiens in the rear....,don't let yer meat loaf

Badss, my car is doing the exact same thing yours was. FP is the same with hose on/or off.

My Crane AFPR is brand new. What do you think is wrong? I already checked for leaks, and there are none.

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'92 Formula
305 TPI
Mods: SLP catback,SLP air foil,ported plenum,Crane AFPR (49psi),MSD6AL,homemade cold air,K&Ns,3:73s,JET fan switch...SLP 1 5/8ths are coming...oh yes

maybe your fuel pressure gauge is broke?? https://www.thirdgen.org/messageforum3/smile.gif

formula - when the Crane was on the car it held the same pressure, then I switched to a Accel (that came with a diapham),, and it held the same pressure as well. I swapped the entire assembly with a new GM regulator (it came assembled - with base and o-rings - $95 - ugh) and "it" started working right. I'm pretty sure the guy that had the car before me messed something up in the base,, how I don't know,, although it sure looked O.K. when I took it back apart. So,, go figure. If there are no leaks around the port fitting, I just don't know what to tell you. Seems like there was a thred on how to check your fuel system to determine if the regulator was "bad" - can find it though.

Maybe a silly question, but where is that vacuum hose?

Best regards, Fredrik

Sounds to me like you figured out the problem...the regulator was going. Also, if you find you cannot lower (or raise) your fuel pressure beyond a certain point AND it is well inside the normal range (39-50)... that too usually points to a regulator problem.

They are like anything else... after time (and miles) they do start to perform less than optimally.

BadSS, you paid $95 for the spring and diaphram? when you say base..what exactly are you referring to? I got the spring and diaphram replacement for $30 from Advanced Auto today.

Thanks guys. I hope the problem will be solved.

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'92 Formula
305 TPI
Mods: SLP catback,SLP air foil,ported plenum,Crane AFPR (49psi),MSD6AL,homemade cold air,K&Ns,3:73s,JET fan switch...SLP 1 5/8ths are coming...oh yes

[This message has been edited by theformula (edited October 23, 2000).]

Hey. Just to update you guys..the problem was similar to BADSS. I replaced the spring and diaphram with a new one and the problem went away. Woo hoo.

By the way guys, get it from Advanced Auto. it's only $29..compared to the dealers $95 price. The pressure however stays at 48..with hose off it's at 52 . I turned the bolt 2 times and i didnt get past 48psi with hose on. Is this normal?

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'92 Formula
305 TPI
Mods: SLP catback,SLP air foil,ported plenum,Crane AFPR (49psi),MSD6AL,homemade cold air,K&Ns,3:73s,JET fan switch...SLP 1 5/8ths are coming...oh yes

The $95 was for the entire assembly - the aluminum base, diaphram / spring, "hat",,, all pre-assembled. I had to remove the old regulator (whole thing) from the fuel rails and replace it with the new unit (it came with new o-rings for the rails).

Formula - I had swapped diaphrams as you did with no luck. However, sounds like your swap helped a little, but I think the fuel pressure should drop approximately 1 PSI for every 2" of vacuum,,, but that's not exact - mine drops 7 PSI (42 to 35) with 18" of vacuum.