Stalls on uphill start - PeachParts Mercedes-Benz Forum

pleiades · #1 12-16-2013, 08:10 AM

So here's a new one, that I think confirms that my (slightly) rough idle note is fuel related, perhaps with the lift pump.

Started the car on a moderately steep hill, put it in drive as soon as oil pressure came up, and it died! The parking brake and main brakes were still applied, so it wasn't from load, it was entirely due to height differential between the tank and the motor.

Started it back up, waited a few minutes, and she drove off fine. I haven't had any issues at all with lack of power (cruises up as fast as I'd like on the freeway) and I just replaced both filters and the in-line filter fuel lines. Going to throw in a can of Startron next for good measure, probably drain the tank and clean the strainer once it's run down toward empty.

It's amazing what minor problems crop up in 30 year old cars... problems you don't see in most other vehicles because they don't last long enough to manifest.

RavenTBK · #2 12-16-2013, 08:35 AM

I'd look for air intrusion from between the filter head and the hardline. The slightest air leak there could allow the fuel to drain back to the tank when parked nose up.

On level ground, the tank is actually higher than the plumbing, keeping fuel up near the lift pump by way of gravity.

Since you were able to restart the car rather quickly, that tells me the lift pump itself is fine, properly drawing fuel up the lines.

I'd inspect all rubber... from the hardline to the lift pump, and from the lift pump to the filter head.

Also check the hand primer. If you've got the plastic headed twist lock type, they've been known to leak, especially after 30 years.

HtH..

Smoker · #3 12-16-2013, 09:12 AM

Right after i did my cylinder head swap mine would start, stumble, die. Then restart, repeat if put in gear.

The first time I just let it warm a little and off we went, then I tracked down a couple of fuel leaks. It got better. Found one more, got better.

Now if it's started on a really cold day without the block heater it starts right up, gives a bit of a hiccup fairly quickly, then settles in, so still an air leak somewhere. Gonna do primary filter and hoses when I replace the a/c compressor this coming weekend.

vstech · #4 12-16-2013, 09:41 AM

go to the dealer, and order the 3 clear lines and the washers... then pull your intake manifold and change them.
odds are good it's the line from the lift pump to the fuel filter, but it could be any of them.

pleiades · #5 12-16-2013, 10:46 AM

Those clear lines are next up, and the braided injector return lines. Are the clear lines a specific part? I'd think that any same-sized hose would fit on the banjo nipples.

I also don't see where the intake manifold fits in... this is on the 617, not the 602.

Thanks all for the ideas.

vstech · #6 12-16-2013, 10:55 AM

yeah, on the 617 the manifold is not in the way.

I've never tried to change JUST the hose, I replace the entire assembly, fittings and all from the dealer.

Diesel911 · #7 12-16-2013, 02:31 PM

Quote:

Originally Posted by pleiades

So here's a new one, that I think confirms that my (slightly) rough idle note is fuel related, perhaps with the lift pump.

Started the car on a moderately steep hill, put it in drive as soon as oil pressure came up, and it died! The parking brake and main brakes were still applied, so it wasn't from load, it was entirely due to height differential between the tank and the motor.

Started it back up, waited a few minutes, and she drove off fine. I haven't had any issues at all with lack of power (cruises up as fast as I'd like on the freeway) and I just replaced both filters and the in-line filter fuel lines. Going to throw in a can of Startron next for good measure, probably drain the tank and clean the strainer once it's run down toward empty.

It's amazing what minor problems crop up in 30 year old cars... problems you don't see in most other vehicles because they don't last long enough to manifest.

Since thev 1981 300SD is the only one you have that is around 30 years Old I am guessing that is the one that is having the issue.

Park it on a Hill again and try pumping a lot on the Hand Primer. If that works it is likey your Fuel Supply/Lift Pump is having issues.

The replacement Valve Kit fot the Lift Pump is cheap and if you scrounge up an O-ring for the Push Rod inside of the Pump you have done a compete rebuild on the Pump.

Old Style Hand Primers with the shiny Alumium body can also be problematic and cause Air Leaks. I don't know if a worn out would could cause the Fuel to magrate back to the Tank or not.

I also don't know if the Fuel Pressure Relieve/Overflow Valve could have a hand it the issue.

Partially Plugged Tank Screen. I don't know if that can have an effect either.

I don't remember how much but there is a spec for a Vacuum Reading on the Fuel Inlet side of the Fuel Supply/Lift Pump and that is easier to set up then a Fuel Pressure Gauge is.

cooljjay · #8 12-16-2013, 08:11 PM

Pull your fuel pressure relief valve on the injection pump and stretch the string out to 27mm I believe it was....As others said its an air leak problem....make sure you have a new primer and also check the fuel lines under the tank....may also look at the rack damper bolt too...