Hard start when warm

[gavio]

Hi All:

I did a search and can't seem to come up with advice on this particular issue. Truck in question is my semi-trusty (downgraded from it's previous rating of trusty!) 83 G20 van with N/A 6.2.

The deal is that I just had the IP rebuilt, and fuel system cleaned out and new filter, etc, then left town on a road trip to Oregon where I am doing some work for a client for about 3 weeks. After the 600 mile trip up here which was mercifully uneventful, and about 10 days of random driving around here, which has also been trouble-free, suddenly......

If I go to start it when it is warmed up, it will have to crank for an insanely long time, frequently requiring several tries. I emphasize that this began suddenly yesterday.

It still starts normally when cold. The glow plugs cycle normally both when cold and hot (i.e. they cycle for a shorter time when hot, but it isn't hot enough for them to not cycle at all). It runs about like always once it's running.

When I try to start it, I get the best results by hammering the throttle down while cranking, so once it starts, it of course belches a great cloud of white smoke, which clears quickly.

Only peculiar thing I've noticed is that once it does start, it sounds quieter than usual for a few seconds, like with less diesel hammer than normal - this may be a symptom of the build up of extra fuel while cranking, though, as it recovers quickly.

As I mentioned, it still starts normally when cold.

Can this be related to weak electrical somehow? But if so, why would it come on so suddenly - literally not a problem, then BING!, a problem.

Anybody have some idea about wassup here?

Thanks, as always.

[gavio]

I once had a warm start problem that was due to a bad starter and this is different in that it happens when the van is just warmed up, but not even very hot - first time it occurred, the van had only been driven about 15 minutes or so and ambient temps here in Florence, Oregon were hanging at around 65F - not exactly a blistering summer.

[john8662]

My first suggestion would have been to check the dragging starter, because cranking speed hot makes a big difference in starting ability once the engine is hot and doesn't get glow.




Only peculiar thing I've noticed is that once it does start, it sounds quieter than usual for a few seconds, like with less diesel hammer than normal - this may be a symptom of the build up of extra fuel while cranking, though, as it recovers quickly.


This makes me think that you've still got an air leak somewhere.

When I had a small air leak on the return hose OUT of the pump the engine would stumble shortly and smoke for a little bit, then all-of-a-suddend smooth out and idle up like normal. This was only seen on hot starts. Turned out to be a small leak at the fuel return hose. Just replaced the spring-type clamps with regular 'ol hose clamps and solved that problem.

I hate to say it, but sometimes a rebuilt pump (exchange) will have more problems than the one you sent in. Had this happen with an exchange rebuilt pump, did the exhange at the local pump shop because I was in a hurry, installed it and it worked fine. Week later, hot start, so bad that I had to tow the heavy burb back home for further diagnosis. With no glow (electronic controller) and hot, it wouldn't start AT ALL. Took pump off, they tested it, was bad. Replaced, problem solved... So, it can happen!

[gavio]

Thanks, John, I'll check the possile air leak situation.....Since it starts so well after sitting all night long, I'd kind of ruled that out,but these are complex and mysterious beasts sometimes.

After a couple days of running errands in Eugene, I've begun to suspect a charging issue......Check it:

If I run it for a bit on the highway and then park it for a while, when I come out it'll start up easily, but if I only drive a few minutes in town and park it, it'll be hard to start. If it sits for longer, it'll get easier to start (presumably the subsequently longer glow time helps here). I tried some experimenting and it seems that keeping it out of overdrive (i.e. higher revs) on the intown driving alleviates the problem a little - but I could be imagining that.

The good news is that it should be easier to get diagnosed......plus (most importantly), it won't keep from getting back home to California next week if I can't get it handled while I'm here.

Sound right?

[gmctd]

If the IP has a black Stanadyne label, it's a good candidate for rebuild - hot-start syndrome can be caused by excessive head\rotor clearance, cured by rebuild to blue-label specs.

[ZZ]

More than likely; the engine needs glow plug heat to start warm. I've had several 5.7L & 6.2L Diesels that had this problem. My easy fix was converting the glow plugs to work manually with a toggle switch.

[john8662]

Gavio,

Well, the diagnosis on charging could sure point to slower cranking speed after it's been driven.

Perhaps a test of your alternator is in order?

But more easily checked, if you've got a slipping belt, that's yer cause!

The alternator and A/C belts are among the hardest to keep tight and not squeeling, especially on 82-84 engines with the pressed steel pulley (although better in the long run, cause the pulley doesn't fail like the newer does).