How do I prime the fuel system on a 1987 300D? - PeachParts Mercedes-Benz Forum

Diesel Dan · #1 09-02-2006, 08:30 PM

I'm in the final stages of a greasecar conversion, and can't get the car to start. Everything appears to be hooked up properly. The directions from greasecar said to prime the fuel system, but the instructions were for an older model Mercedes with that white plastic manual primer pump. My car has no such device. Is there any sort of manual primer for my car, or do I just have to crank it? Thanks for any words of wisdom, or personal experiences with this phase of the the conversion.

- Dan

TheDon · #2 09-02-2006, 08:34 PM

i belive the 87's have a self priming system.. just crank away.. wait for someone with better advice on that one... all i know is the 87's are self priming.. which i do not envy

Carson357 · #3 09-02-2006, 08:39 PM

just fill the filter with diesel and priming is not needed

Motorhead · #4 09-02-2006, 08:45 PM

Quote:

Originally Posted by Carson357

just fill the filter with diesel and priming is not needed

I always hold the throttle down to prime faster. If it doesn't start after trying these two steps, crack three injector lines at the injector and hold the throttle down while cranking. BE CAREFUL with your starter that you don't overheat it.

Brian Carlton · #5 09-02-2006, 08:53 PM

Agreed. Crack all six injector lines and crank it with your right foot on the floor. It may take a total of two or three minutes of cranking to get fuel out of the hard lines. Give the starter a break or two during this process. You'll probably need a second battery. Once fuel starts dripping all over the head, tighten the hard lines and start the engine.

Palangi · #6 09-02-2006, 09:09 PM

Dang, there must be a hundred threads on here about folks not being able to get 603's restarted after opening up the fuel system. There must be some way we can Southern engineer a small hand operated pump spliced into a hunk of fuel line for priming a 603 like a 617. I wonder if the button style hand pump from a w115 300D could be adapted for this purpose? Thimk!!! There has to be a better way to do this.....

Brian Carlton · #7 09-02-2006, 09:30 PM

Quote:

Originally Posted by Palangi

Dang, there must be a hundred threads on here about folks not being able to get 603's restarted after opening up the fuel system. There must be some way we can Southern engineer a small hand operated pump spliced into a hunk of fuel line for priming a 603 like a 617. I wonder if the button style hand pump from a w115 300D could be adapted for this purpose? Thimk!!! There has to be a better way to do this.....

I'm not sure if this would be successful. It certainly would be desirable for those folks who don't fill the secondary. But, once the system is full, all the pumping in the world is not going to displace any air that is currently in the IP. The only way to do that is to rotate the IP.

The 603 seems highly sensitive to any air being introduced to the IP and getting rid of it is difficult.

Hatterasguy · #8 09-02-2006, 10:23 PM

I don't understand what the problem is, crank the car it will start.

I have changed the fuel filter a number of times on the 603/6 series engines, don't see why all of a sudden we are seeing a bunch of posts on this subject.

lrg · #9 09-02-2006, 11:49 PM

I've gotta agree with Hatty. Fill the fuel filter and crank away. It usually starts in 20-30 seconds but if not pause a couple of minutes after every full 45 seconds of cranking to let the starter cool. It's not a big deal.

retmil46 · #10 09-03-2006, 12:14 AM

Recently had the intake manifold off for cleaning, and all the hard lines pulled off to replace the o-rings in the delivery valves on the IP. Once done, I left the hard lines cracked at the injectors and didn't reinstall the intake crossover pipe.

Luckily I had a second person available to sit in the car and crank the engine as directed. Cranked the engine in 5 to 10 second bursts, with at least a 20 second wait in between, to keep from overheating the starter and killing the battery. The second person would continue this routine until I saw fuel spurting out of another injector, I would yell at them to stop, ram a shop towel down beside the injector, then tell them to continue with the routine. Did this until we had fuel coming out of all six injectors. Took about 5 minutes.

Then torqued down all the hard lines at the injectors, reinstalled the intake crossover pipe, and tried starting the engine. Didn't even take 5 seconds, fired right up smooth as you please.

I did remember to remove the fuel-soaked shop towels before starting the engine.

Diesel Dan · #11 09-05-2006, 11:38 AM

Thanks to all who replied! I topped off the fuel filter and cracked open the banjo bolt on the return part of the fuel filter housing and cranked a few times to let any air out of the system. Then I tightened that back up and cranked for about 4-5 short cycles of cranking, and it started! I was originally worried about doing all that cranking, but thanks to the advice I got on this board, everything worked out just fine. I sure do wish there was a manual primer though - my poor battery! Not to mention the starter!

matt87_300d · #12 09-05-2006, 01:38 PM

Quote:

Originally Posted by Hatterasguy

I don't understand what the problem is, crank the car it will start.

I have changed the fuel filter a number of times on the 603/6 series engines, don't see why all of a sudden we are seeing a bunch of posts on this subject.

The problem is that this is not always the case. As we all know, 20 year old cars all have their quirks, and it seems that some have an easier time starting theirs than others. I was the one having trouble the other week with this; I had filled my filter ~70% and had a really bad time starting the car--like MINUTES of cranking.

Other things that were suggested to help the process include having a full tank of fuel, and I would park the car downhill, as well, to increase the pressure from the fuel tank, thereby helping the pump do its work.

Don't give up too soon--it takes seemingly FOREVER to get them started (at least on mine).

lrg · #13 09-05-2006, 02:03 PM

One trick I've learned with both my cars is that it helps to change the filter when the engine is still warm. Needless to say anything to make it fire off a bit easier is helpful and I found I do a lot less cranking when it's still warm.

Jadavis · #14 09-18-2006, 09:30 AM

Quote:

Originally Posted by Diesel Dan

I sure do wish there was a manual primer though - my poor battery! Not to mention the starter!

When you did the conversion did you add an electric lift pump? You could have cracked a line before the IP and run it to fill the feed lines. It would have saved you a bit of cranking.

-Jim

Diesel Dan · #15 09-18-2006, 12:18 PM

Quote:

Originally Posted by Jadavis

When you did the conversion did you add an electric lift pump? You could have cracked a line before the IP and run it to fill the feed lines. It would have saved you a bit of cranking.

-Jim

Last time I opened the fuel system, thus introducing air, and causing a need for priming, I followed someone's advice from this board, and attached a manual hand siphon pump to the hose leading to the IP, and sucked the fuel all the way to that point. I then had to do only minimal cranking to get the car started. Good idea - save my battery/starter.

I think I've seen your user name in reply to one of my many postings on either this board or the Greasecar board. You installed an electric Holly Blue pump on your 300D, right? I've heard that if you install an electric pump in the engine compartment, it will burn out due to the heat, and the fact that it is pulling the fuel rather than pushing it. Have you had any problems with pump burnout?