M103, bad fuel pressure regulator? - PeachParts Mercedes-Benz Forum

John5788 · #1 07-30-2009, 01:31 AM

I've been having a starting problem with my car, but never really cared to fix it until now.

sometimes after I've let my 1993 2.6 sit around for more than 4 hours, the car becomes hard to start. I let the fuel pump prime, and I start cranking it. the engine does not start, OR if it does, it immediately dies. on the second try though, the engine kicks on after the first starter click.

does this sound like a bad fuel pressure regulator to you?

tinypanzer · #2 07-30-2009, 04:36 PM

I'd start by making sure the plugs aren't fouled.

A fuel pressure test would be needed to verify a bad FPR.

Oracle12345 · #3 07-30-2009, 05:01 PM

I would check fuel pressure then go from there

lkchris · #4 07-30-2009, 05:12 PM

The M103 at its age has mostly leaking injectors.

They flood the motor making it hard to start when hot/warm.

Verify by trying next time with throttle depressed a little.

Replace old leaking injectors and don't worry much about pressure regulator.

Cal Learner · #5 07-31-2009, 07:45 AM

Can't the FPR be checked quickly and easily by simply pulling the small plastic tube off it while engine idles to see if fuel comes out of FPR? If yes, the diaphragm is bad and FPR needs to be replaced.

Oracle12345 · #6 07-31-2009, 08:13 AM

Quote:

Originally Posted by Cal Learner

Can't the FPR be checked quickly and easily by simply pulling the small plastic tube off it while engine idles to see if fuel comes out of FPR? If yes, the diaphragm is bad and FPR needs to be replaced.

Not really more involved

tinypanzer · #7 07-31-2009, 05:23 PM

You'd know if the diaphragm was torn, but that's about it. If it WAS torn, however, you'd be sucking gas into your intake and it would be hard for that to escape notice.

pawoSD · #8 07-31-2009, 06:07 PM

Mine does the exact same thing....eventually when my car $$ pool builds back up (its been heavily drained lately

) I will throw new injectors on mine...

Oracle12345 · #9 07-31-2009, 07:12 PM

Quote:

Originally Posted by pawoSD

Mine does the exact same thing....eventually when my car $$ pool builds back up (its been heavily drained lately

) I will throw new injectors on mine...

I would check fuel pressure first before replacing anything. The orginal posters problem sounds like a fuel pressure problem. Could be anything such as the fuel pump not putting out the normal volume of fuel, enough pressure, leaks in the system, internal and external.

pawoSD · #10 08-01-2009, 01:58 AM

Yes, but a weak pump would cause other issues, my car starts fine if it has been off long enough to cool a bit....or when started from cold....its just those few hours after sitting starts that are harder. I found that giving the pedal a press as its cranking will allow it to fire right up. It also starts right up as long as it has been under 1.5 hours or so since it was shut off. Its not a huge deal, it starts within 2-3 seconds even when cranky....(pun intended

) and if I just stop and give a second try, it always starts right up on the second try. I'm not worried....and have no current plans to touch the injectors. It needs tie rods first...

John5788 · #11 08-02-2009, 12:23 AM

how much fuel pressure should I be seeing and where should I be measuring it from on the fuel distributor? what do I replace if the fuel pressure is bad? fuel pumps?

my injectors are brand new as of around march, so thats not the problem. holding the throttle open while cranking the motor does not help.