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+--- Thread: Om603 revs when started (/showthread.php?tid=7814)
Om603 revs when started - chrisbrixp - 07-26-2017
Good morning fellas,
Got a brief question for a laxed Wednesday morning.
I just aquired an 87 300td and I am in the middle of servicing and inspecting the issues and mal-maintanece on the vehicle.
After doing an oil change, the valvetrain became noticeable noisy, this led me to the lifters needing a cleaning. I remove the turbo pipe that crosses over the valve cover and then the valve cover. Leading to my point. Once removed it, I wanted to start the vehicle without the valve cover and crossover pipe, and the engine revved up on its own. I have done the exact procedure on many other diesel including an na 606. Newer 6.0 powerstrokes and old 6.5 gm detroits.
Does anyone have an explaination to why it'll rev up on its own? Is it the electronic control looking for airflow thru the maf? Almost like an runaway but still ignition controllable.
Thanks for the input,
Chrisbrixp
RE: Om603 revs when started - NZScott - 07-26-2017
Does it actually have a MAF? EDC pumps weren't around til the 90s weren't they? I'm not that familiar with 603s, but only reason I can think of is the throttle is stuck somehow, the vacuum high idle is on (if fitted) or it's sucking a secondary fuel in from somewhere.
Is it revving to max RPM or just idling high? If the throttle is adjust for idle the idle governor can be overcome by throttle input so will rev as it pleases sometimes
RE: Om603 revs when started - STDGer - 07-28-2017
I m not in a 603 too, but what about ur throttle linkage? Maybe it is hookd a littlebit?
Another idea is, stick the cable for (dont know the exact word) cold start raising off the ip.
Maybe ur airfilter is so close that u didnt notice it bevore?
Greetings from germay
RE: Om603 revs when started - chrisbrixp - 07-28-2017
(07-26-2017, 10:48 PM)NZScott Does it actually have a MAF? EDC pumps weren't around til the 90s weren't they? I'm not that familiar with 603s, but only reason I can think of is the throttle is stuck somehow, the vacuum high idle is on (if fitted) or it's sucking a secondary fuel in from somewhere.
Is it revving to max RPM or just idling high? If the throttle is adjust for idle the idle governor can be overcome by throttle input so will rev as it pleases sometimes
I though so also, but it has a sensor mounted below the air box similar to my om602 engine. My 95 e300 does not have the sensor from what I recall. I checked the linkage to the throttle but didn't seem to catch anything out of place.
It would just keep climbing once I started it, got to about 2500 rpms when I shut it off. Then I checked the linkage and restarted, and same thing, an instant rev.
Its as if there is a brick on the throttle pedal.
It reminds me of a gasoline car with a vacuum leak.
Maybe there was restriction in the air intake system and the linkage was adjusted to compensate.
RE: Om603 revs when started - NZScott - 07-28-2017
Disconnect the throttle ball linkage on the IP and see what happens. I have a feeling if it still revs up the "course idle" (I think they call it) is adjusted too high
RE: Om603 revs when started - EvoPeter - 08-17-2017
If its not the throttle linkage it could be a stuck element.
RE: Om603 revs when started - chrisbrixp - 11-07-2017
Okay, so I'm still stumped.
I replaced the turbo and "rebuilt" the lifters. I still haven't installed the crossover tube or the dummy tube that replaced the trap ox.
It will not start now, I'm going to check compression but timing is spot on.
It was running before I pulled it apart, now it almost seems as if it just fast cranks but not firing at all.
Maybe the head gasket failed allowing oil into the cylinders causing a momentary run away, and now no compression?
There isn' very much suction from the intake when it' cranking if I place my hand over it.
Also, what is the purpose of the maf sensor? Will it cause the engine to not start if it doesn't sense any flow?
I thought it was used for idle control, and egr.
Honestly, I didn' think an 87 diesel could be so complicated.
RE: Om603 revs when started - raysorenson - 11-07-2017
Rebuilt the lifters? They were revised after '87 to fix the noise.
The stock '87 head gaskets do cause oil leaks but almost certainly not a runaway. The oil galleys can leak pressurized oil into the timing cover and leak down the back of the engine. Replacement gaskets have this problem fixed too.
The maf (actually a VAF, vane air flow)can't cause a no-start. It's only for EGR AFAIK.
Cranks fast? Does it sound fuckity while it's turning over? That could be compression. You say timing is spot on, are you talking about the pump or the cam or both? Hydraulic lash adjusters can pump up, killing compression.
RE: Om603 revs when started - chrisbrixp - 11-07-2017
Thats my only consideration. I was able to get to glow plug hole on cylinder one and install my compression tester. Didn't register anyhing on the gauge for compression. Place my finger over the hole. Wouldnt even push enough pressure to push or suck my finger.
I just disassembled the lifters and ran the parts thru an ultrasonic cleaner. I did pump them in oil before i installed them back in there respective bores. But I reassembled them and installed over a month ago. I would think if they were pumped up, they would have relieve pressure by now. Is there a procedure to deflate the lifters if that's the case.
I was referring to the mechanical timing marks on the harmonic balancer and camshaft. They are on point. The camshaft cant be 180* off, the lobes on cylinder one are facing up. And I believe the crank pulley only can go on one way. Plus I didn' remover the cam gear, just zip tied it in place. So i just looked at the marks to verify it was correct.
RE: Om603 revs when started - chrisbrixp - 11-23-2017
Just to potentially close out this thread, I changed all my lifters with "ina" brand tappets/lifter. after i installed the cam and turned it over to check timing. I had instant compression in the cylinders. Got it to run and idle, so no i have to finish assembling the engine and see how it runs.
Already sounded alot quieter. we'll see.
Thank for all the input!