603 Starts, Runs for 5 seconds Then Quits
 

A friend of mine's 87 300D had to be towed home today. The car has been very well cared for and he is the second owner. While driving home in city traffic the car lost power and the engine quit. We checked the fuel filter, prefilter and air filter and all were OK. The car starts up immediately runs for 5 seconds then shutters and stops. Once it fails, you can restart it but it again only runs for 5 secs or so and quits. The prefilter is full of fuel and so is the main filter. No debris noted in either. Any ideas on the next thing to check to get her running again?

Try loosening the fuel cap on the diesel tank. I have seen it gives similar symptoms. Also I think there is a vent mechanism on tanks of some of the D models.

Next thing, if your car has a hand pump, its probably loose or not screwed in correctly. Unscrew the hand pump, and nicely screw it back on and hand tighten it to your best strength.

Third possibility is the Glow Plug relay is quitting in just 5 seconds, so you loose that glow and it dies on you.

Good luck. Let us know what you find.

MVK

Don't forget to check the fuel tank screen. There is no primer pump on the 603 motors. It's primed simply by cranking.

We opened the fuel cap and that didn't help. No vacuum was noted in the tank upon opening the cap. When I removed the fuel prefilter the fuel kept coming from the tank feed so I don't think the tank screen is the problem either. It has about 3/4 of a tank of fuel and draining the tank to check it would be a real chore. Any place where air could be entering the system besides the normal fuel filter connections? We didn't notice any fuel leaking when this occurred. It was very warm yesterday (90+ degrees) could that have anything to do with it? Haven't heard of vapor lock on a diesel!!

You may have a fuel pump going bad or (shudder) injection pump. It's more likely you have something more simple happening.

The cheapest thing to do at this point is go ahead and change the fuel filters, especially the spin-on main filter. It may be full of fuel but its the FLOW of fuel that is important. When you change this filter fill the new one with fresh fuel after you get it positioned almost in place to bolt on. I say this because if you fill it first and then try to get it into position to install, you might have to slide it into place sideways and spill all the fuel.

This is the cheapest thing to try first - and if the main filter hasn't been changed in the last 30k miles its probably due.

Good luck - hope this helps.

Ken300D

I would have a look at the main fuel filter. Pour the contents into a glass jar so you can see what's in it. (Water, gasoline, mud)? Also, could be sucking air. I understand 603 fuel filter has an O-ring which is critical. Maybe a 603 owner can comment on that.

The o-ring is under the pipe where the suction line enters the pump (after the pre-filter). Fuel usually siphons back into the tank if this o-ring is bad, and you get VERY hard starts or start and die problems. Worth a check, it's cheap and the IP is NOT.

You probably have the IP full of air if it has been leaking, and you may want to crack the injection lines at the injectors (14 mm) and crank until no more air comes out after you change the filters and the 0-ring. I'd change the o-ring first and see if you can get it to run, takes forever to prime that beast on the starter. Plan on charging the battery once at least if you have lots of air!

If you have had not other running problems, most likely it is the o-ring leaking. However, a plugged main filter will do exactly the same thing -- no pressure in the IP, no fuel in the sleeves, no delivery. If it is the filter, plan on replacing it again soon, and check the pre-filter for color. If it turns black again in a day or too, you need to have the tank cleaned, you have algae in there plugging the screen and filters.

Peter

Thanks PSFRED
 

I think the next step is to replace the o-ring since we replaced the main fuel filter this morning and that didn't help. The main filter looked OK and the fuel in it was clean. Ditto for the prefilter. This car was owned by a MB tech since new and has only 89K miles on it. It is very clean... no drips, leaks and wetness anywhere under the hood. I checked Fastlane for the o-ring PSFRED mentioned but couldn't find it. Does anyone have a part number for it? Is this an o-ring that could be replaced by a standard o-ring from a hardware shop or is it a one of a kind part. The reason I ask is we don't have a MB parts supplier readily accessible here in Key West FL.

Check to make sure the cutoff lever stays up when you start the car, too -- if the vac switch on the dash is bad, it will stop as soon as the vac comes up! If this is the case, the temp fix is to unplug the vac line on the shutoff, and stop the engine with the lever (big pain, but better than not running!)

If the lever stays down with no vac on the shutoff, you should wait until someone with professional advice answers -- it could be a serious IP problem, and you should NOT mess about with this pump.

The o-ring can be replaced by one the same size from an assortment.

Peter