Weight saving: Remove fuel pump!
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TECH Fanatic
Joined: Dec 2001
Posts: 1,220
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From: Germantown, MD
Weight saving: Remove fuel pump! I say this as a joke cause some friends and I were working on my fueling issues and some of the wierdest stuff happened.
First off, With my rising rate reg, we hooked up a bike pump to the vac line(on the reg) and pumped in about 40 psi which takes my FP up to 100. You would think this ould choke the engine out right? Well it didn't. Absolutely no change in idle. We even later on drove with the FP that high and it drove like normal. Even with rice_etr behind me, he said that my pipes looked clean and no smoke coming out.
Secondly, at one point we removed the reg and just ran the fuel line stright to the rails. The first time we did this without the gauge hooked up(as my gauge connects to the FPR). So we pull the fuse to the Fuel Pump and let the car run so the pressure is relieved. Over a minute later, the car is still running. So we disconnect the power lines to the top of the fuel tank. The cars still ran!!! WTF!?!?!?!
How can the car run when there's no power going to the fuel pump?????
Later on we did the same test, but we hooked up the fuel pressure gauge. Pump was putting out at least a 100psi. We cut the power to the pump, and the FP dropped slowly. The engine idled fine till about 10 psi of fuel when it finally cut off. So this time it acted normally. We tried it again and again, when the gauge is hooked up, the car dies out like it's supposed to.
We checked the lines for restriction and there is no obvious restriction. Granted we didn't have the tools to simulate heavy flow.
Summary: The pump can't keep up. At WOT it's lucky to maintain 60psi(sometimes dipping as low as 40). I have a Walbro GSS340. Mightymouse, Rise-Etr, and myself racked our brains Saturday trying to hash this one out.
There are two issues: One the pump doesn't seem to have the flow. Is it restriction in the line? Is the pump defective? It shouldn't be voltage as the pump is seeing 12.9V when the car is on.
The second issue is tuning. Why isn't my car dying out when I up the FP? The computer has no control over FP. How is it compensating for the immediate rush to a super rich condition?
I know this is a lot to read, but thank you.
Mike
First off, With my rising rate reg, we hooked up a bike pump to the vac line(on the reg) and pumped in about 40 psi which takes my FP up to 100. You would think this ould choke the engine out right? Well it didn't. Absolutely no change in idle. We even later on drove with the FP that high and it drove like normal. Even with rice_etr behind me, he said that my pipes looked clean and no smoke coming out.
Secondly, at one point we removed the reg and just ran the fuel line stright to the rails. The first time we did this without the gauge hooked up(as my gauge connects to the FPR). So we pull the fuse to the Fuel Pump and let the car run so the pressure is relieved. Over a minute later, the car is still running. So we disconnect the power lines to the top of the fuel tank. The cars still ran!!! WTF!?!?!?!
How can the car run when there's no power going to the fuel pump?????
Later on we did the same test, but we hooked up the fuel pressure gauge. Pump was putting out at least a 100psi. We cut the power to the pump, and the FP dropped slowly. The engine idled fine till about 10 psi of fuel when it finally cut off. So this time it acted normally. We tried it again and again, when the gauge is hooked up, the car dies out like it's supposed to.
We checked the lines for restriction and there is no obvious restriction. Granted we didn't have the tools to simulate heavy flow.
Summary: The pump can't keep up. At WOT it's lucky to maintain 60psi(sometimes dipping as low as 40). I have a Walbro GSS340. Mightymouse, Rise-Etr, and myself racked our brains Saturday trying to hash this one out.
There are two issues: One the pump doesn't seem to have the flow. Is it restriction in the line? Is the pump defective? It shouldn't be voltage as the pump is seeing 12.9V when the car is on.
The second issue is tuning. Why isn't my car dying out when I up the FP? The computer has no control over FP. How is it compensating for the immediate rush to a super rich condition?
I know this is a lot to read, but thank you.
Mike
Re: Weight saving: Remove fuel pump! i decided that somebody snuck a crappy inline pump onto your car without you knowing. thats restricting the good pump at wot and keeping it running at idle.. thats all i got to add lol
test again with everything hooked up normal, but remove the vaccum reference from the regulator and verify it is still droppign from 60 at wide open. if yes then replace the pump or up the voltage to it and try again. if you have to get a new pump and that doesnt work, then its gotta be that small fuel filter?
test again with everything hooked up normal, but remove the vaccum reference from the regulator and verify it is still droppign from 60 at wide open. if yes then replace the pump or up the voltage to it and try again. if you have to get a new pump and that doesnt work, then its gotta be that small fuel filter?
