Fuel Pressure

[SonomaGTlover]

I know this doesn't pertain to most of you on here but thought it might post some good information that has not come up in my searches.

Anyway... As some of you know, my SoGT was loading up at NATS and I never made a decent pass. The best being a 16.1 and I was hoping to at least be in the 15's. A couple guys helped me out to diagnose the problem and it appeared that the fuel pressure was too high. Well, I have a different set-up than the SY/TY's (not any better for sure) and more pressure is required. I have little poppet nozels going to each cylinder that require 50lbs. just to open them up so the 60lb reading we got wasn't bad. It turns out that it was the very early stages of going bad. This is a common problem with this set-up and often requires replacement anytime after 75,000 miles according to some of the S-Series members. How fortunate was I to get 162,xxx out of mine. I knew about the possibility but it seemed to be fine before the Vortec upgrade. I guess with the highter flow from the Vortecs and headers it became more noticeable.

The assembly runs around $300 but I was lucky to find just the regulator for $40 (it seems this is the part that fails). I ordered it imediately and hope to have it by the weekend. Once I get it installed and make a few street passes I'll let you all know how it went. Maybe I'll make it to Gateway a few times this year?

 

[schrgds]

Re: Fuel Pressure

What year is your truck?
I see you're cpi so its different sorry.

 

[SonomaGTlover]

Re: Fuel Pressure

I have the '92 CPI "W" and the cheapest I can find the whole assembly is through a friend at a GM dealer for $243 I believe it was. They're roughly $250+shippingon Ebay so I'm trying just the regulator for now. After that I plan to do the nut kit cause that is deemed second to fail.

 

[jimmyz79]

Re: Fuel Pressure

Jon,

Replace the whole thing (and the nut kit), not just the regulator. I just did my 93 Sonoma CPI and I noticed that the tubes on the old one were very brittle. The new replacements are supposed to be a better design than the originals. After I replaced mine, it seemed to cure alot of evils that the engine had. The L-35 seems to sing at speed, but I wish it had more grunt on the low end. I've put a enhanced chip in it (some board member did it for me a couple of years ago), and I did the EGR plate mod and it is somewhat better, but I believe the cam profile hurts the 1/4 mile times....

 

[SonomaGTlover]

Re: Fuel Pressure

Jon,

Replace the whole thing (and the nut kit), not just the regulator. I just did my 93 Sonoma CPI and I noticed that the tubes on the old one were very brittle. The new replacements are supposed to be a better design than the originals. After I replaced mine, it seemed to cure alot of evils that the engine had. The L-35 seems to sing at speed, but I wish it had more grunt on the low end. I've put a enhanced chip in it (some board member did it for me a couple of years ago), and I did the EGR plate mod and it is somewhat better, but I believe the cam profile hurts the 1/4 mile times....

Thanks for the tips:tup: I've inspected the nut kit and it all seems pretty good. The regulator however appears to have been tampered with and I know I tampered with it at NATS trying to correct it. I plan to replace everything next year sometime so I'm patching at this point. $50 compared to $300 allows me to mod as much as possible before I tear it all apart again and build it right.

I already have plans for a chip. Did you have your EGR deleted with the chip? The guy that has been SOOO helpful with my build is running low 14's with stock heads and 12's with juice. I did notice that my truck flows plenty of air with vortecs and headers so I hope to be a little quicker when it's dialed in.

Here's a tip for you....
If you want more response at lower rpm's do this quick and simple mod to your IMTV. Around 2600-3000 rpm this opens up allowing more air. I'm sure you can feel a boost in power around that rpm range. Drill the holes or cut the flaps off all together to have that air available all of the time. Every little bit helps.

Check out the link in my sig for lots of pics during my build. I should have more recent ones posted but never got around to it.

The cam profile is very close to the popular 412 (I think that's right) cam upgrade for the SY's. There is a thread here somewhere with all the numbers.

Thanks again

PS...if anyone else has any ideas why my truck might be loading up I'd love to hear them. The FPR for this set-up is NOT suposed to be adjustable. With the new one I will keep the original setting until I get the problem solved. I'll experiment with the adjustment and timing later.

 

[vortecfiero]

Re: Fuel Pressure

when i was using my CPI i had a K&N and a free flowing exhaust

i had my FP set at 5lbs more than stock (so about 55 psi)
i dialed in about 2 to 3 degrees more advance

in my 2600 lb car this made a noticable difference across the board
and the most dramatic difference was in the lower RPMs

i tried a manual switch on the plenum door and found that opening it
at about 500 rpm sooner made a difference

the ecm also closes the door at about 4000 to 4500... i left mine open
a little longer but at 5000 it was better closed and pulled to 6000 nicely

craig

 

[jimmyz79]

Re: Fuel Pressure

No, didnt delete the egr. The guy put about 4 degrees advance, seemed to help, he said he could of gone more. He also said he increased line pressure on the trans, its a 4L60E, don't think the 92's had that trans.

What size holes should I drill in that throttle door?????

Thanks, Matt

 

[SonomaGTlover]

Re: Fuel Pressure

No, didnt delete the egr. The guy put about 4 degrees advance, seemed to help, he said he could of gone more. He also said he increased line pressure on the trans, its a 4L60E, don't think the 92's had that trans.

What size holes should I drill in that throttle door?????

Thanks, Matt

I'm pretty sure I used 1/2" but it really doesn't matter. I didn't want to remove it all because i still wanted it to function normal.

And...YES you are correct I do not have the "E" tranny.

i had my FP set at 5lbs more than stock (so about 55 psi)
i dialed in about 2 to 3 degrees more advance

This may be a stupid question...
Do you keep the timing set at "0" and the advance is what the EMC creates? I played around witht he timing on my truck and it seemed better around 2-3 degrees+ at idle but it's back to "0" now. Maybe that is where I need to look next for my issues? I want to get this backfire/loading up issue solved before I turn Dynosources loose on the programming. I am really hoping that it's just the regulator.

Oh yea, did you adjust your fuel pressure with that little security torx screw in the regulator? I believe "clockwise" to increase pressure?

Thanks guys

 

[vortecfiero]

Re: Fuel Pressure

This may be a stupid question...
Do you keep the timing set at "0" and the advance is what the EMC creates? I played around witht he timing on my truck and it seemed better around 2-3 degrees+ at idle but it's back to "0" now. Maybe that is where I need to look next for my issues? I want to get this backfire/loading up issue solved before I turn Dynosources loose on the programming. I am really hoping that it's just the regulator.

Oh yea, did you adjust your fuel pressure with that little security torx screw in the regulator? I believe "clockwise" to increase pressure?

Thanks guys

i did a NO-NO lol i removed the regulator from the assembly and "compressed" it about 1/16" carefully in a vise using a socket to contact the body of the canister only and it worked

i dialed in the initial 2 to 3 deg advance with the distrubutor. You will know you have too much when the lower RPM is awsum and the 4500 to 6000 feels down on power

craig
btw i still have my CPI set up if anybody is interested... PM or email me

 

[bucwildbob]

Re: Fuel Pressure

i have the vortec.. i can tell you all about that peice of shit. effing money pit. if you are having a lot of problems with it missing under a light load and backfires possibly through the intake or just random missing.. bad idle.. its the lifters. the lifters go out on all 4.3s about 180k miles. it caused me probably about a yr worth of searching. i finally figured it out and fixed it then through a rod bearing. right now i think i have a lifter going out again. I left that valve open and noticed a loss of power so i left mine stock. the cpi is completly adjustable as far as fuel pressure goes, you just need a really small security/tamper proof torx bit. i jump the fuel relay and change mine, its a pain in the ass though cause you have to take the upper plenum off any time you want to change it. the 4l60 came in 94 some late 93s had them. raising your timing raises your base timing. the computer will adjust it to a point. i would suggest raising your base timing about 4 degrees. i ran a 15.7 with a 4 door with bad lifters. im about halfway done collecting turbo stuff now. 96+ intake and injector system with mega squirt and a stock td06-17g for the time being

 

[SonomaGTlover]

Re: Fuel Pressure

i have the vortec.. i can tell you all about that peice of shit. effing money pit. if you are having a lot of problems with it missing under a light load and backfires possibly through the intake or just random missing.. bad idle.. its the lifters. the lifters go out on all 4.3s about 180k miles. it caused me probably about a yr worth of searching. i finally figured it out and fixed it then through a rod bearing. right now i think i have a lifter going out again. I left that valve open and noticed a loss of power so i left mine stock. the cpi is completly adjustable as far as fuel pressure goes, you just need a really small security/tamper proof torx bit. i jump the fuel relay and change mine, its a pain in the ass though cause you have to take the upper plenum off any time you want to change it. the 4l60 came in 94 some late 93s had them. raising your timing raises your base timing. the computer will adjust it to a point. i would suggest raising your base timing about 4 degrees. i ran a 15.7 with a 4 door with bad lifters. im about halfway done collecting turbo stuff now. 96+ intake and injector system with mega squirt and a stock td06-17g for the time being

That's some good information... It's the first I heard of bad lifters. Somehow I don't think that's my problem since I have vortec heads from a '99 that the seller claimed to have only 34,xxx miles racked up. It was rolled down a ditch and got parted out. I will certainly have it checked if the regulator doesn't clear it up. I'd hate to put new heads on an old tired engine. Looks like I'll be doing a complete rebuild if I do.

I'm making a list of all possibilities and checking them out one by one. THANKS

 

[bucwildbob]

Re: Fuel Pressure

to change the lifters you take off upper and lower intake, take off valve covers and rocker arms, pull up push rods and pull out lifters. a lot of people i know with about 180 on stock lifters have the same damn problem. most cant pinpoint it however. did you notice much diff going to the 96+ heads? thats the project im working on this month. and figuring out a fi system that will suppor the turbo sitting here in my room

 

[SonomaGTlover]

Re: Fuel Pressure

to change the lifters you take off upper and lower intake, take off valve covers and rocker arms, pull up push rods and pull out lifters. a lot of people i know with about 180 on stock lifters have the same damn problem. most cant pinpoint it however. did you notice much diff going to the 96+ heads? thats the project im working on this month. and figuring out a fi system that will suppor the turbo sitting here in my room

Changing the lifters is no problem at all, but I am wondering if maybe I have a lobe that is a bit worn down causing the valve to not open all the way and closing prematurely? Timing chain possibly? It does seem to smooth out a bit at 2- degrees plus? The lifters are all the same in the 4.3's... rollers right? I'll have to check some part numbers.

If I go far enough to buy new lifters I may as well get the good ones and have the heads completely re-done so I know the valvs are seating good. If I do the heads and lifters I will need to do rings to prevent blow-by and should probably get a new cam to eliminate the possibility of a bad lobe. New rings require removing the pistons and so on... As you can see I may as well just rebuild the entire block and do it right from the beginning. My purpose at this point was to get the modifications done and working properly before I spend $5-$7K on the engine.

I appreciate the feedback and believe me.. It's in my notes. If the regulator doesn't do the trick, I may try to find a low mileage set of lifters somewhere to see if it helps. What troubles me is that EVERYTHING was perfect (or seemed to be) before I changed heads so the lifters/cam should still be OK. Unless the vortecs flowing almost twice the air would enhance a problem like this that would normally be unoticeable.

Anyway, I'm expecing my regulator Monday since i didn't get it today. You never know with todays mail though. You can bet that it'll be installed and tested the same evening I receive it. I'll post a follow-up with the results.

 

[SonomaGTlover]

Re: Fuel Pressure

did you notice much diff going to the 96+ heads? thats the project im working on this month.

Actually... even with this issue I am having the truck picked up .7 in the quarter. Some of that will be the headers and full dual exhaust but I am sure they work together. There is no sense in having heads that flow twice the air if the exhaust can't get get it back out.

 

[bucwildbob]

Re: Fuel Pressure

the vortec cam is more agressive. and if you are going to replace lifters, its a good time to through a better cam in. The cam you have is most likely fine. the lifters are roller hydraulic so virtually no wear should be on the cam at all. timing set.. its most likely good as new. I took mine apart (part of trying to find the problem) and it looked brand new with 200k miles on it. you can change all that stuff with the motor in the truck.. bottom end.. the motor has to come out. freshen up the top end and drive it till it blows!

 

[super-gt]

Re: Fuel Pressure

Actually... even with this issue I am having the truck picked up .7 in the quarter. Some of that will be the headers and full dual exhaust but I am sure they work together. There is no sense in having heads that flow twice the air if the exhaust can't get get it back out.

where'd you get your headers from?
-taylor

 

[SonomaGTlover]

Re: Fuel Pressure

where'd you get your headers from?
-taylor

I got them from Headman. I have another set but they are the shorter ones. They come down along side the block at the same angle as the stock exhaust but about 4" further. Here's a picture. As you can see they have already been modded to fit the Vortec heads. (the sensor holes are in a different location) Since that pic was taken they have been painted with High Heat Ceramic paint. Also I had to fabricate a crossover pipe and you will too with these headers. The difference is that you won't have to modify the tranny mount like I did in the second picture. You can cross over in the stock location in front of the tranny.




I can post a better pic of them if you are interested. They are made by MrGasket/Eagle Performance Part# 1451 and listed to fit 4.3L Chevy S-10 (originally sold in late 80's) I still have the original box for them. I was told when I bought them that they'll fit but I have never had them on, just mocked up on the engine stand.

I was going to put them on Ebay but never got around to it. Opening bid would have been $75 with $150 Buy-It-Now. If you are interested let me know. Otherwise you can check out Headman or Edelbrock.

 

[super-gt]

Re: Fuel Pressure

hmm..I may be interested, i will get back to you on that.

-taylor

 

[SonomaGTlover]

Re: Fuel Pressure

Well, although the FPR helped out a little I still have an issue.:rant: It was mentioned that without the O2 sensor inthe exhaust that it would run rich causing a backfire. Another possibility may be the lifter/rocker assembly.

I am thinking it may have something to do with the lifters as Bucwildbob suggested. Although I never removed the lifters and kept the pushrods in order the rest of the head assembly is different. Since everything ran perfect before I changed heads, before I tear the intake off again I am considering one more possibility.

I mounted the Oxygen sensor about 6" further back in the exhaust pipe and it's not fully welded in cause i wasn't positive I wanted to keep it there. Also I did it the night before NATS. I have an exhaust leak at the header coupled with the tiny gap on either side of the sensor bung. Would this have anything to do with the functionability of the sensor? Does it matter that I only have 3 cylinders feeding it instead of all 6? Also, since it was further back, I needed to make an extention on the wiring. I cut the wires on the sensor pigtail and extended them to keep the plug accessible. Should I have extended the harness wires to the plug and left the sensor pigtail alone? Maybe the sensor is bad?

Thanks guys...Free decal of choice to the one with a working solution. I'm getting desperate.

 

[TurboTony]

Re: Fuel Pressure

I haven't read the whole thread, it's late, I'm tired, I'll do that tommorow.

To answer the questions though,

Yes, an exhaust leak anywhere before the sensor is bad, get it welded in properly.

Soldering the wires on the o2 sensor renders it garbage. The sensor "breaths" to get its sample air reference through it's pigtail. Soldering the wires up seals the air path. Extend the harness and buy yourself a new sensor. I'd recommend an AC delco sensor as well. Some of the aftermarket ones cause nothing but trouble.

Tony