Fuel pump problem ...

[Leo Rojas]

Hello everyone, I'm new around here. I am from Costa Rica and I own a Mitsubishi Colt GT with a 4g63t engine swap.

Last Friday my fuel pump (outside the tank) broke. The engine stopped after stuttering a bit and wouldn't start again. I called my mechanic and he said that my fuel pump had a leak and when I tried to start the car a lot of fuel was leaking. On Saturday, he took out the pump, which was very strange because it said "125 psi max" and my mechanic said that my car doesn't need all that fuel pressure, so I went with my mechanic and bought a BOSCH 80 psi fuel pump that should be enough for my car.

On Monday, my mechanic installed the pump and the engine started but when I hit the gas full throttle the car just doesn't go, it moves faster when I take my foot off the throttle !!! When I barely touch the gas it keeps reving to less than 3000 rpm and then does the same thing.

My engine is a 4g63t with K&N air filter, front mounted intercooler, bigger fuel injectors, fuel pressure regulator, HKS SSQ BOV, Greddy Electronic Boost Controller running at 10 psi with a TD05 turbo, Greddy turbotimer, Denso Iridium Spark Plugs, OML 10 mm racing silicone wires, stock ECU and stock internals.

Any help ? Could it be more gas or less than required ? Suggestions ?

Thanks,

Leo

 

[DSM90AWD]

Don't think the pump itself (unless defective) would be causing you the issues you have. More likely install error:
- Pump installed backwards
- Return line not re-installed
- Hose connections bad
- Fuel filter clogged/defective or pinched fuel line.

Also what is your base FP set at? Did it change with the new pump?

FYI.. according to THIS the Bosh Pumps don't flow under low pressures (compared to other HP aftermarket pumps), but excel in the higher pressures

 

[Leo Rojas]

Thanks for your reply.

Today my mechanic is checking the installation again and is also installing a fuel pressure gauge, because I have a FPR but no gauge. With that I can have a better idea about the base FP.

I also checked that link but I don´t know what I should do about that .... Should I increase FP ?

 

[Leo Rojas]

If it helps my BOSCH Fuel Pump Part Number is 0580254911.

 

[DSM90AWD]

The link was more to give you some general info on aftermarket DSM pumps. I cannot find specific information on the pump you list, but would likely flow less than a 190lph (likely at 150lph) as it's an OEM replacement on several Ford Cars with <200HP.

I'm still leaning towards installation error. Lets see what your mechanic finds first before modifying fuel pressures.

With the gauge in place you should be able to easily see whether you have too little/much fuel pressure. If too much, then need to reduce base fuel pressure and/or look for restrictinos to the return line. If too little, then the pump is defective, the fuel filter is clogged or the FPR is defective.

Base pressure is 37-38psi (vacume line disconnected) for a 1G and 42psi for a 2G. Not sure how you've "converted" to the 4G63, but the ECUs are factory calibrated to 450cc injectors at the above stated base fuel pressures

 

[Leo Rojas]

Ok, I called the BOSCH dealership and they don´t know the flow of the fuel pump. They said that this exact pump is found in Mercedes-Benz with 2.6 - 3.2 6 cilinder engines.

I'll have news from my mechanic this evening.

 

[Leo Rojas]

Yesterday I spoke with my mechanic.

He says that at idle the FP is constant at around 40 PSI, but when I hit the gas full throttle the FP drops to about 25 PSI. After adjusting the FPR, the car revs to about 3k rpm and then stops working right (if I barely touch the pedal), but If I hit the pedal ful throttle inmediately stops pushing.

He says that the FPR and the fuel filter are both OK. We think that maybe the BOSCH fuel pump doesn't have the flow that my car needs.

Could that be the case ???

 

[DSM90AWD]

I still think the pump though marginal should at least get you around. Have you checked the voltage at the pump? May need to "rewire" using a larger gauge power If pump requires more amps.

FYI.. Walbro (the DSM Std Pump Upgrade) makes a 190 and 255lph inline pumps for ~$140

 

[Leo Rojas]

Thanks for the tip.

I'll tell my mechanic to check the voltage at the pump.

Which one of the Walbro pumps is a better choice ? The 190 LPH or the 255 LPH ?

 

[DSM90AWD]

If you have an aftermarket AFPR then go with the 255lph, if not, and not running over 400WHP, stick with the 190lph.

The 255 tends to overrun the stock FPR (small diameter bypass oriface) at idle/low rpms where fuel consumption is lower and pump output is high

 

[Leo Rojas]

Ok, great.

Tomorrow I'll check the voltage at the pump and if necesary I'll make the electrical changes.

I have an aftermarket FPR so I think I'll be getting the 255 Walbro.

I'll keep you informed

 

[Leo Rojas]

After spending all afternoon with my mechanic here's what happened.

We checked the voltage at the pump and there were some problems with the wiring. After fixing them, we adjusted the FPR and now the car runs better than ever.

I even tried it @15 psi of boost (normally I have it @10 psi) and even over 6000 rpm the car keeps going strong.

Thanks, DSM90AWD