Tuning With CJM Fuel & Vortech...Pres Drop
09-30-2007, 06:02 PM
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Tuning With CJM Fuel & Vortech...Pres Drop
There was a thread in the past with a couple guys, myself included that had fuell pressure issues with the CJM return fuel system and Vortechs. Pressure would drop up high in the rpms. Did anyone figure a way to fix this or work around it?
09-30-2007, 09:54 PM
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We just finished installing the CJM Stage 2 Fuel Return System with the Vortech SC, 550cc injectors on a RevUp Z. No fuel pressure issues noted. It has been steady at 42 to 50 psi all the way to redline after an initial drop of about 2 psi at the beginning of WOT. Not sure if the Stage 2 with the stainless steel hardpipe (delivering fuel to the rails) makes a difference. It is about 50% bigger in cross-section than the stock line.
09-30-2007, 10:00 PM
#4
I kinda wonder if this has to do more with how much power/fuel you need. A 350whp setup will probably have perfect fuel pressure with a CJM setup while a setup with more power will start to drop the pressure
I'm still not sure what's really causing it. When I replaced my entire fuel pump assembly and GTM reinstalled my CJM the way they always have, it seemed to give me an additional 5 or 10 psi or something like that, making the pressure more capable of being consistently tuned.
But mine still does drop a little. We didn't bother really digging into what the issue was since the setup was good enough to tune with.
The stage 2 line didn't help in my case as me and others have predicted, but I just wanted to eliminate that as a possibility
I'm still not sure what's really causing it. When I replaced my entire fuel pump assembly and GTM reinstalled my CJM the way they always have, it seemed to give me an additional 5 or 10 psi or something like that, making the pressure more capable of being consistently tuned.
But mine still does drop a little. We didn't bother really digging into what the issue was since the setup was good enough to tune with.
The stage 2 line didn't help in my case as me and others have predicted, but I just wanted to eliminate that as a possibility
Last edited by sentry65; 09-30-2007 at 10:02 PM.
10-01-2007, 02:06 PM
#7
At the same time....many many more guys have no issues at all with thier systems that are the same or very simular . Seems there has to be something different with the few guys that are having the problem . Sentry even states going to the stage2 fuel system didnt help much . My first thought is there maybe a restriction some where....dont know just a thought .
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10-01-2007, 02:24 PM
#9
Originally Posted by sentry65
Barzten1 and I both have aug 02 build dates, no idea what'd be different though if anything. Just an odd coincidience
I guess the bucket assembly in the tank is still stock also .
Last edited by booger; 10-01-2007 at 02:38 PM.
10-01-2007, 03:36 PM
#10
It's probably your Walbro! I had a bad Walbro, and I chased around my dropping fuel pressure for a while.
you can check your pump this way:
disconnect the return line from the fuel cannister. Use an -AN fitting and length of hose to extend the return line so that you can run the return line into a measured container. In theory, your Walbro 255 pumps out approx 1 gallon/minute. At idle, your engine is using very little fuel and most of the fuel pushed my your pump is getting sent through to the return line.
What I did was to extend the return line so it will dump into a 1 gallon gas can. Then, I started the car and let it idle for exactly 1 minute. At the 1 minute, turn off the car. go and see how much fuel got pumped into the walbro. In my case, I only has about 1/3 of a gallon.
I swapped my pump with a new Walbro, and all works great!!!
you can check your pump this way:
disconnect the return line from the fuel cannister. Use an -AN fitting and length of hose to extend the return line so that you can run the return line into a measured container. In theory, your Walbro 255 pumps out approx 1 gallon/minute. At idle, your engine is using very little fuel and most of the fuel pushed my your pump is getting sent through to the return line.
What I did was to extend the return line so it will dump into a 1 gallon gas can. Then, I started the car and let it idle for exactly 1 minute. At the 1 minute, turn off the car. go and see how much fuel got pumped into the walbro. In my case, I only has about 1/3 of a gallon.
I swapped my pump with a new Walbro, and all works great!!!
10-01-2007, 07:38 PM
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Yeah I told Todd who was helping me with the fuel issues I wanted to try a whole new bucket for the assembly. We put in another one but it was used. We blew out the filter to make sure there was flow and it wasn't clogged. He disasembled the fuel pressure regulaor to make sure it was ok. He's pretty much gone through the whole fuel system a couple times and says there is no reason for the fuel pressure to be dropping.
10-01-2007, 10:27 PM
#17
if a new assembly helped the situation, that is a sign of a clogged internal filter. that is the only thing in the pump assembly that could cause a problem, unless your regulator plug o-ring is not sealing, that would allow pressure to internally leak back into the canister.
supercharger cars will max out the fuel system quite a bit sooner, but i would think that 450rwhp would most likely be no problem for the setup... hard to say, but turbo guys can get mid 500s out of the stage 1.
its only blower guys having this fuel system capacity problem from what i have seen, which makes me tend to believe that its close to maxing out the fuel system if its being picky about fresh filters etc. There is no where to go wrong in the hoses/rails/etc for the setup. The aeromotive regulator is very simple and reliable and i have never had anyone need me to replace one yet.
sounds like the pump itself is close to maxing out, and right about the point where a single walbro is maxed out, i think the stock 5/16 hardline used in stage 1 kits is going to become a setback, and also the stock canisters internal plumbing as well, as its not very open in there, i have taken them apart.
if you need anything from me, feel free to contact me via PM or email and I will do whatever I can.
supercharger cars will max out the fuel system quite a bit sooner, but i would think that 450rwhp would most likely be no problem for the setup... hard to say, but turbo guys can get mid 500s out of the stage 1.
its only blower guys having this fuel system capacity problem from what i have seen, which makes me tend to believe that its close to maxing out the fuel system if its being picky about fresh filters etc. There is no where to go wrong in the hoses/rails/etc for the setup. The aeromotive regulator is very simple and reliable and i have never had anyone need me to replace one yet.
sounds like the pump itself is close to maxing out, and right about the point where a single walbro is maxed out, i think the stock 5/16 hardline used in stage 1 kits is going to become a setback, and also the stock canisters internal plumbing as well, as its not very open in there, i have taken them apart.
if you need anything from me, feel free to contact me via PM or email and I will do whatever I can.
10-01-2007, 10:55 PM
#18
my car runs fine so I'm not really concerned with the fuel pressure issues right now. The pressure isn't ideal, but it works well enough. 
I'll have to figure out something else in the future if I go with a built block
I'm just sharing my experiences to help Barzten1 out
I'll have to figure out something else in the future if I go with a built blockI'm just sharing my experiences to help Barzten1 out
10-02-2007, 04:39 AM
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yah, still racking my brain on this one, i have gone though everything a few times now...
swapped new walbro
disassembled fuel pump assembly, insured all lines connected properly
swapped in new fuel pump assembly
inspected all line
disassembled fpr and inspected
swapped vacuum sources to fpr
while revving the engine, the fuel pressure immediately jumps from 42 to 60ish, then towards the higher rpm, takes a quick littl dive to 20psi! While doing a pull, the same thing happens, right around 5200rpm, the fule pressure starts to drop....
swapped new walbro
disassembled fuel pump assembly, insured all lines connected properly
swapped in new fuel pump assembly
inspected all line
disassembled fpr and inspected
swapped vacuum sources to fpr
while revving the engine, the fuel pressure immediately jumps from 42 to 60ish, then towards the higher rpm, takes a quick littl dive to 20psi! While doing a pull, the same thing happens, right around 5200rpm, the fule pressure starts to drop....