92 190E 2.3 suspect fuel pump weak/dead - PeachParts Mercedes-Benz Forum

vstech · #1 03-05-2013, 11:50 AM

where can I test fuel pressure/volume?
the car is EXTREMELY difficult to start, and when cold it WILL NOT accept throttle without starving for fuel and dieing.
I have replaced one fuel pump, and the fuel filter, but not the other pump. my guess is the upper pump is for idle, and the lower pump is for highway, or educate me if I'm wrong. the two pumps could be one and two stage pumps...
either way, at idle until the motor warms up, the car just sits there once it's FINALLY gotten started.

also, how do I go about setting the timing? I cannot find a balancer indicator on the crank.

where should #1 plug be on the cap? it's currently at 7:00 standing in front of the radiator.
firing order would be nice also.
thanks!

ps2cho · #2 03-05-2013, 12:26 PM

I believe it still has the 4cylinder fuel distributor right?

Measure fuel volume at the return line to measure pump volume output.

From what I understand, two pumps is simply to even flow and provide some extra backup power. They do not have independent functions.

mbdoc · #3 03-06-2013, 07:19 AM

John, fuel pressure is measured at the cold start injector, approx 85 psi.
Also should deliver 1 Qt in about 25 seconds on the return line.

The distributor rotor should align with the punch mark on the outer housing.

Have you checked the over voltage relay?

vstech · #4 03-06-2013, 07:21 AM

Yes. Ovr fuse intact. I will measure fuel flow, thank you for the locations.

ps2cho · #5 03-06-2013, 10:25 PM

Quote:

Originally Posted by mbdoc

John, fuel pressure is measured at the cold start injector, approx 85 psi.
Also should deliver 1 Qt in about 25 seconds on the return line.

The distributor rotor should align with the punch mark on the outer housing.

Have you checked the over voltage relay?

Bosch specs are 1L (or Qt close enough) in 40seconds for CIS-E...

Does the 4cylinder pump more volume than the 6cylinder CIS-E?
Just want to clarify since 25 vs 40sec is a big difference...don't want to have you spend money that is not needed!

mbdoc · #6 03-07-2013, 07:08 PM

All of the CIS-E cars should deliver 1L or 1 Qt in less than 30 seconds.

97 SL320 · #7 03-07-2013, 08:54 PM

Fuel flow is dependent on operating pressure with free flow rate being higher than flow at operating pressure. Measuring at the return line post regulator will properly load the pump.

ps2cho · #8 03-08-2013, 12:14 AM

from the MB factory manuals they state 1L in 40sec...
http://w124-zone.com/downloads/MB%20CD/W124/w124CD1/Program/Engine/103/07.3-5701.pdf

Do you suggest 30seconds should be the maximum limit? Would 40sec show injection issues compared to 30sec? I'm just interested for future reference...
I know that with two brand new Bosch fuel pumps on my old 260E and a rebuilt distributor, I got 1L in 26 seconds...Is it even possible to beat that?

daddi · #9 03-08-2013, 01:10 PM

Start by replacing this sensor A0085423217

It's failure has the same exact symptoms as you describe.

vstech · #10 03-08-2013, 02:08 PM

Quote:

Originally Posted by daddi

Start by replacing this sensor A0085423217

It's failure has the same exact symptoms as you describe.

What is this part called. your part number brings up nothing I can look up.
Do you have an MB part number?

daddi · #11 03-08-2013, 02:34 PM

A0085423217 is the MB part number.
It's called Sender unit continuous injection system.

You will only find at the dealership, it's not expensive.

97 SL320 · #12 03-08-2013, 08:20 PM

Looks like the coolant temp sensor for the computer and gauge

ps2cho · #13 03-08-2013, 10:39 PM

It can be found at other places, not just the dealerships so save yourself some money if you want to replace it for good measure.

You are correct though, it is the coolant temp sensor for the CIS-E computer. There is another coolant temp sensor that is strictly for the cluster.

My experience with the coolant temp sensor -- Difficulty to start, but ZERO influence when warm, starting or not as long as it is warm, the car runs fine. I broke a pin off (older 3-pin unit used in 87 vs 4 pin for later but same principle) and the difference was immediate the following morning when I had to drive to work. I already knew I broke the pin so I knew what changed. If this is consistent with your issue, I say go for it.

vstech · #14 03-31-2013, 07:56 PM

ok, I changed the sensor, no difference.
I pulled the harness off, and it had oil all over it, so i cleaned out the harness and attached to the new sensor. no change in starting.
I checked the fuel pressure and flow, and it was great to the distributer and out of it. there is a metal can that looks like a filter on the return line out of the distributer, is that a problem possibility?
the fact that it works perfectly once it warms up but is nigh impossible to keep running or start it when it is cold is baffling... it's gotta be in the air mass sensor/ or the computer itself... why is it SOOOO hard to keep running? even the slightest throttle, and it stalls.

vstech · #15 03-31-2013, 08:00 PM

I suppose the throttle position sensor failing would cause similar symptoms as well...