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Old 05-22-2008, 03:34 PM
JBG JBG is offline
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Join Date: Jun 2007
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Start Car, jerk/hard idle


Recently, on two occasions, I've started the 300 TD wagon (1985) and had some odd idling jerks. First time it started fine, warmed up 30 seconds, I took off, drove a few block to a red light, and while waiting at the red light the car started to jerk once about every 10 seconds. Kind of felt like a light kick to the car. It was odd enough that I just drove around the block and parked on a side street, put it in park, it idled fine, then put it back in drive with brake on, and no more spasm. Drove the rest of the day fine, no problems.

The other time was a few days later, this time it started to jerk right after starting the car. My wife was driving it and she just gave it more fuel to warm it up. Seemed fine after that.

We thought it might be grease-related--we've been running a greasecar stock system for about 20k miles. Figured we should up the purge time to 30 seconds (from 25) and drive a little longer to burn up any veggie in the engine before shutdown.

My question is: if it's NOT veggie related, does the problem sound familiar? I.e. timing chain or anything major???? I'm a little freaked out about the timing chain as I don't know what the symptoms are of a failing chain and I know how catastrophic a failed chain can be. What do you think?
1985 TD wagon, 228k
running on grease since 3.07
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Old 05-22-2008, 03:45 PM
vstech's Avatar
Join Date: Mar 2006
Location: Mount Holly, NC
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does not sound timing related.
it does sound like a problem in the injectors. report back after you have added in the purge time on your car.
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Old 05-22-2008, 04:04 PM
rrgrassi's Avatar
mmmmmm Diesel...
Join Date: Jun 2006
Location: Royse City Tx
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Sounds like nailing or fuel starvation, like from air in the system. Like VSTech said, it does not sound like a timing issue.

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Old 05-22-2008, 04:21 PM
winmutt's Avatar
85 300D 4spd+tow+h4
Join Date: Apr 2006
Location: Atl Gawga
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Injectors, air in the line, or possibly poor compression. Right after car start, like runs ok for 10sec and then like crap?
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Old 05-23-2008, 10:43 AM
JBG JBG is offline
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Thank you for your replies, and yes, I'm relieved to hear it's not timing related. Here's the deal now: I've increased purge time to 30 sec. and so far so good, nothing weird. Only thing veggie-related that is still odd and new is when I leave the car on veggie after stopping to run an errand (say 20 or 30 minutes with the car off), after starting right up fine, in about 10 seconds, it starts to bog. I have to hit the fuel pedal and up the RPMS slightly for a few seconds, then it's just like normal.

I don't expect you guys to get into this problem as it's WVO related and I know most of you do not approve. I can always ask this question on the greasecar forum, especially if it continues to be troubling or gets worse. If you have any ideas, though, I'd be curious to hear them.

And about the timing chain: is there any way to anticipate needing to replace it? Symptoms?

Thanks again,
1985 TD wagon, 228k
running on grease since 3.07
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Old 05-23-2008, 04:22 PM
patbob's Avatar
Its a Whatsit
Join Date: Oct 2006
Location: Portland, OR
Posts: 837
An air bubble sucked into the IP at restart might cause that. Ever do it when you properly purge and restart on diesel? If not, maybe try draining the WVO system and flushing & refilling that system with biodiesel. If it still stumbles like that on restart from the WVO system, then it probably isn't WVO related but rather plumbing related.
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