IP and fuel pump questions - PeachParts Mercedes-Benz Forum

coachgeo · #1 05-09-2005, 12:41 PM

First the Diesel IP question (617 and simular Bosch) . If you had an 12v fuel pump that would stay on when the car is off, would it push fuel thru the IP and back down the return line? Would it push fuel thru the injector lines but not activate them (too low a pressure) and continue then flow thru the injector return lines. ?

Now an OEM 617 and other diesel MB's fuel pump question. Can these pumps leak fuel into the oil pan if part of it fails such as a rubber diaphram.

boneheaddoctor · #2 05-09-2005, 12:51 PM

Quote:

Originally Posted by coachgeo

First the Diesel IP question (617 and simular Bosch) . If you had an 12v fuel pump that would stay on when the car is off, would it push fuel thru the IP and back down the return line? Would it push fuel thru the injector lines but not activate them (too low a pressure) and continue then flow thru the injector return lines. ?

Now an OEM 617 and other diesel MB's fuel pump question. Can these pumps leak fuel into the oil pan if part of it fails such as a rubber diaphram.

I would think the answer is yes...becasue think about operating the primer pump...are you not doing the very same thing......

H2O2 · #3 05-09-2005, 02:10 PM

As long as the pump was capable of producing the same or more pressure than the stock feed pump, it would circulate fuel through the pump reservoir and out the pump overflow return line. It wouldn't fill any injector lines because the delivery valves stop any flow upward unless it exceeds the valve's internal spring rate (much much higher than your electric pump). Only the pump plunger and barrel (elements) are capable of building that kind of pressure.

I don't believe fuel can escape the pump and leak into the crankcase, but given that the pump is lubricated by an engine oil feed line, it's theoretically conceivable. The engine probably wouldn't run correctly (or at all) given that the loss of fuel would more than likely cause the elements to lose their prime.

t walgamuth · #4 05-09-2005, 10:46 PM

strange question... hope you're not trying it.

TonyFromWestOz · #5 05-10-2005, 10:32 AM

Quote:

Originally Posted by coachgeo

First the Diesel IP question (617 and simular Bosch) . If you had an 12v fuel pump that would stay on when the car is off, would it push fuel thru the IP and back down the return line? Would it push fuel thru the injector lines but not activate them (too low a pressure) and continue then flow thru the injector return lines. ?

Now an OEM 617 and other diesel MB's fuel pump question. Can these pumps leak fuel into the oil pan if part of it fails such as a rubber diaphram.

Coach,
It is better to connect the electric lift pump to an Ign. or Acc. power source. That way, your fuel pump will not remain on when the key is turned off.
Your battery will also not be drained by the electric pump current draw.

coachgeo · #6 05-12-2005, 01:05 AM

I was wondering about the lift pump leaking cause in many engines if the diaphram in the lift pump ruptures it WILL leak fuel into the sump. There for some DO NOT reccomend a 12v booster pump to aid in pushing thicker veg. oil fuels from the back to the engine bay. This is because the thought is if the diaphram bust in the lift pump then the still pumping 12v booster will push fuel into the sump via the leaky diaphram, thin out the oil and ruin and engine.

My question about fuel being pumped thru the IP when engine is off isss based on the hair brain idea of a small LP RV hot water heater full of wvo instead of water that has a pump in it that occasionaly sends fuel thru the system to help keep the thing from gelling up.

coachgeo · #7 05-12-2005, 11:46 AM

comments?

coachgeo · #8 05-13-2005, 01:52 AM

So everyone agrees then that if an aux. pump was pushing diesel (see txt. diagram below) thru an about to go south, or failed OEM lift pump it would be pretty much impossible for diesel to leak into the oil pan? (on a 617)

TANK--->Aux. pump--->"OEM Lift Pump"---->Filter---->IP

boneheaddoctor · #9 05-13-2005, 08:07 AM

Quote:

Originally Posted by coachgeo

So everyone agrees then that if an aux. pump was pushing diesel (see txt. diagram below) thru an about to go south, or failed OEM lift pump it would be pretty much impossible for diesel to leak into the oil pan? (on a 617)

TANK--->Aux. pump--->"OEM Lift Pump"---->Filter---->IP

I've never torn apart an OEM OM617 pump........so I can't render a judgement on how possible it is to leak if it fails.

coachgeo · #10 05-13-2005, 03:48 PM

anyone else?

coachgeo · #11 05-15-2005, 01:19 AM

Sorry for another bump. Knowing about the chances of aux. pump pushing fuel into sump is a real important question for a wvo'er kinda person. I hope some one can add good .02

Thanx in advance.