beeman

My 85 300sd does not start spinning over and catching on one or two cylinders but not starting. The glow plugs have 12 volts to ground. From an earlier TMAllison post responding to a simlar question advised pumping the hand pump 50 to 100 times but I cannot because fuel gushes out the top under the plunger. After this the engine would not catch at all but spun over with no firing at all. I will crack the lines to the injectors to check for fuel flow and take it from there. I am thinking it is a fuel problem. The car ran perfectly to this point. Any advice would be welcome. Also, how do you stop the engine (a different 300sd) when turning off the ignition has no effect? I cracked the fuel line but that is messy and there has to be a better way.

TMAllison

You need a new hand primer pump as yours is letting air into your IP causing it to continously lose prime.......The new style is ~$20 and works much better than the old ones did.

All 617's have a read "stop" lever on the linkage. Push with your thumb to manually shut off. Have you checked for vacuum leaks feeding the ign?

beeman

Thanks again TMAllison. Vacuum leaks to IGN? IGN? I must plead ignorance again. The new hand pump will be installed. Manual shutoff noted with glee. Thanks again and when ZDMak comes up with the leak down tester I will let you know how the project car is faring.

TMAllison

I would install the primer pump first; sounds like you have a big leak. Certainly sufficient that no fuel, or frothy fuel, may be being delivered to one or more inj's. Hard to compress, pressurize and inj frothy fuel (actually its too easy to compress which is the issue-you get pressurized air inj'd rather than fuel).

Regarding vac: you've been messing around the IP quite a bit. There is a line from the shut offf at the rear that travels to the ign (IGNition) switch which may have gotten knocked loose. From memory, I think it goes up over the top of the oil filter cannister and into the firewall/dash.

beeman

No actually I have not touched anything on this car. It just simply would not start one morning tho' it did unusually quit after starting as it had not before. Following your instructions on another thread that dealt with a similar scenario I gave the hand primer a afew shots only to have fuel gushing onto my hand. This can't be right and so I intend tomorrow replacing the primer from new tho' I have two units on my parts cars, an '80 and an '82. I will buy a new one as I do not wish to dismantle a good running unit if I don't have to. The '80 runs fine and the seal is still intact on the ALDA. This is my ace in the hole so I do not want to tamper unecessarily. I am betting that you are correct in your assessment and the primer will be replaced with new. Meanwhile being a bugger for punishment I am ordering leak down tester and all required tools from Zdmak (Peach parts are down at this time) to get to the bottom of my '82 that will not fire on cyl 5. I need to know why. I have never had a diesel car and I find this experience more interesting and challenging than anything I have seen automotively thus far and I have done the gamut. I really like the 300sd, not fast but satisfying in so many other ways, smooth and great on the freeway, and althuogh dated it has the MB stuff.

beeman

Yes I have fooled with the '82 with the none firing #5 cyl but I have not touched the inj pump in any way. Fools rush in etc. As advised by yourself compression test first. Ta very much for your continued much needed input.

beeman

I replaced the primer pump with the newer Bosch unit (had to make up a crow foot) removed the fuel line to the filter and the line coming into the hand pump. The line(vacuum) going back to the firewall also became disconnected. Hand pump was pushed several times but the engine does not start or even cough. Vapour comes up thru' the air cleaner. I turn the engine for ten seconds and wait ten minutes but there is no change. The glow plug on light and the sound signal do not work.

beeman

Does this system self prime? There must be a lot of air in the system now.

TMAllison

Not self priming; hence the manual pump.

Pump manually until you hear fuel moving to the IP. Then crank while cracking lines open at the IP until fuel leaks from each in turn to prime. My 85 will actually pump enough fuel manually that I can make the braided return lines weep......others claims theirs won't do that.

Then give it a good shot of WD40 in the intake "while" trying to start with hot GP's and a fully charged battery so it spins fast.

beeman

I went back to square one and checked out the glow plugs again with the relay unplugged and found a bad plug based on no continuity and another that tho' there was continuity it just didn't jump to zero and in fact didn't quite make it to zero. These plugs were changed and the engine started and ran fine. Oh happy day. I will replace all glow plugs.

TMAllison

Ruling out the basics is always the place to start on a diesel. No heat, constricted air flow or frothy fuel can confuse the issue and seem like something different oftentimes.

Are we gald we were talked out of pulling the PC's now?

beeman

Yes I am glad. Gladder still when yesterday I replaced all glow plugs and the light goes on for glow and the engine catches right off. Very glad indeed. On my '85 with the #5 dead cylinder I am waiting for a leak down tester before taking any thing apart.