Electric fuel pump questions.

[theman53]

I am and always have been having problems with EGT. I stopped at a cummins shop yesterday and he couldn't believe I wasn't running a lift pump. He said in the truck world you can't make power without one on the VE pump. I explained they didn't take much fuel and he said it doesn't matter. That if you mash it at idle you loose all the advance until the pump picks up enough fuel to make up for what you have lost when punching it. He can show this under load with a timing light attachment. This is exactly the situation I have as it doesn't have snap off the bottom but when the pump is pulling good it does fine. I guess for those running a lift pump and others who know what is a good pressure to run these at? He said the 6B needs around 14psi to do the job all the time. What do you think we need?

[truckinwagen]

I have run a low pressure lift pump for a long time( about 5-7 PSI) and have always been happy.

not only does it help with performance, but it will keep you from getting air leaks as often.

-Owen

[R.O.R-2.0]

I am and always have been having problems with EGT. I stopped at a cummins shop yesterday and he couldn't believe I wasn't running a lift pump. He said in the truck world you can't make power without one on the VE pump. I explained they didn't take much fuel and he said it doesn't matter. That if you mash it at idle you loose all the advance until the pump picks up enough fuel to make up for what you have lost when punching it. He can show this under load with a timing light attachment. This is exactly the situation I have as it doesn't have snap off the bottom but when the pump is pulling good it does fine. I guess for those running a lift pump and others who know what is a good pressure to run these at? He said the 6B needs around 14psi to do the job all the time. What do you think we need?

i bet we could do just fine with 5-10 psi of pressure at the pump inlet.. these things dont flow much fuel thru the pump.. it takes like 5-6 minutes to get a quart out of the return line at idle..

[theman53]

Which is why I think if we had more flow to the pump we could have more pressure or more going through the return. At least it would be there if we needed it. I am unsure if it will work, but I will try it and see sometime. I am thinking if a holley blue pump is diesel rated I will see what 9psi will do.

[R.O.R-2.0]

they make a green shaker pump thats diesel rated, and puts out about 6-8 psi without a regulator..

[regcheeseman]

How about a yamaha bike fuel pump? Any one off an FZR would do.

Nice compact unit that sits at 4 psi.

But I don't believe that it'll make any difference, the standard vane pump could flow a large volume of fuel, the amount of fuel injected as you 'mash the throttle' is so small in comparison that the pressure drop would be miniscule/ neglible.

Providing the vane pump is working properly.

[theman53]

If I understand correctly the VE pump is about as opposite from the CIS injection system as can be. Our VE ramps up timing as the internal pressure rises. The vane pump is the only thing pulling fuel so when you do mash it from idle even if the pressure stayed the same as the engine RPM increased you wouldn't gain timing. Therefore you would lose response. I am thinking of putting about 14psi to it and change nothing else. See what happens, the worst I think that could happen is all the fuel would go through the out bolt back to the tank and I would be thinner in the wallet

[R.O.R-2.0]

its still going to inject the same amount of fuel.. the regulator inside the pump isnt going to be letting any more fuel flow to the pump head than what it has now.. if it does, the governor will take care of it and bring it back to where it should be..

tyler pressure fed one of these pumps with pretty high pressure, and the advance curve DID NOT CHANGE.. that tells me that its not going to help any..

cummins VE pumps have like 7/16ths supply line to them, and still need a lift pump.. they MOVE ALOT MORE FUEL.. and use alot more fuel..

our engines move almost no fuel, and burn even less of it..

on my engine, i only noticed an improvement because my pump was shot. and it made it super easy to start.. i was more fond of the primer function, rather than anything else..

[RabbitJockey]

actually giles has said before it will increase the fueling to a certain point, he didn't say how much.  i was just reading daves 19 page franken thread haha, gotta read over that once in a while

[truckinwagen]

having taken a cummins VE pump apart, I can tell you that the vane pump in one of them is exactly the same as the one in the VW pump.

they will move the same amount of fuel as the VW VE pump.

it has more to do with the fact that the fuel system up to the pump is functioning under vacuum(for lack of a better word) and everything from the tank to the pump is a restriction(filter, hoses, water separators) by feeding the pump pressure, you are assuring that it is not starving for fuel, especially at higher throttle/RPM.

[theman53]

I know it won't change the curve, but it won't let it fall.

EX: say pump pulls 6psi worth of fuel, you stab it and it either stays at 6psi or goes down to 3psi. Then you don't see any advance until the pump is spinning 2,000rpm and pulling it back up to 6psi then it starts advancing and then making more power. If you have the inline pump pushing the 6psi you stab it it never goes below 6 psi and the advance starts right away. The numbers maybe way off as I think the internal pump pressure at idle should be 43psi or something. But the difference between the 2 sides of the pump gives the advance. If the suction side falls or stays static at all my THEORY is that it will give me the problems I am having.  ALSO, I think if I had a lighter car like MK1 rabbit and or a taller ring and pinion my issue wouldn't be as noticable. With my 3.67 R&P and the MK2 jetta I think the extra to get going and up in the RPM range is making what I have going on worse.

I am also going to run 3/8" line from the tank up to make sure that I don't have any flow restriction. Like I said, it will either work or send it all back through the out bolt and make no difference at all.

This is my theory and I think my EGT situation and gutless off idle is because of this. I want to put more fuel to it to get it to move and it does after it gets moving, but under 1,500 it is useless. Above that it works ok. guessing around 2100rpm and up it is real good around 2500 rpm I think I am making 6psi boost and then it is fine until max boost and EGT go crazy.

[theman53]

Anyone find me an adjustable fuel pressure regulator rated for DIESEL that doesn't cost over 100.00?

[R.O.R-2.0]

Anyone find me an adjustable fuel pressure regulator rated for DIESEL that doesn't cost over 100.00?

diesel is nicer than gas to rubber seals..

anything rated for gas should happily take diesel..

[theman53]

I don't know. Seems to me like diesel and rubber don't get along. Maybe I have just had bad luck? I have always had trouble unless it was diesel rated stamped on the rubber or stating it was OK

[R.O.R-2.0]

i used to clean my motorcycle oil filter elements in diesel, forever.. then one day we didnt have any, so i soaked it in gasoline, and destroyed the rubber seals in no time.. it was amazing the difference between the 2 solvents

besides, doesnt gas come from higher up on the evap tower at the refinery?

that means they refine diesel even more to get gas from it..

i dont see how diesel would be any worse than gas.

i can leave a seal sitting in diesel for weeks, with no problems. throw that same seal in a container of gasoline, and BAM! its twice as big, and super duper soft..