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Tractor Talk Discussion Forum

Chevy 250 Cid engine problem..

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Mike Burdick

07-24-2005 09:14:49




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I have a pickup with a GM 250 Cid engine, 6 cylinders – carburetion.

About a week ago it suddenly started running badly and then I noticed the oil pressure gauge dropped to zero. I immediately shut the engine off and towed the pickup back to the ranch.

A couple of days later I had time to look at it and started it. The oil pump immediately had the required pressure but the engine still ran badly – like it was out of time. I retimed it (it was okay by the way) and started it but it still ran rough.

I took the compression in each cylinder and all were even and within specification. I removed the pan and looked at the oil pump and it was fine.

Do any of you have some clues as to what is happening or what I should check out next?

Any help and/or advice would be greatly appreciated…

Mike

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Mike Burdick

07-31-2005 08:40:01




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 Re: Chevy 250 Cid engine problem.. in reply to Mike Burdick, 07-24-2005 09:14:49  
The problem turned out to be a broken push rod - it had 3/16" broken off the top. I replaced it along with the lifter valve and now the engine is running fine.

Thanks everyone for your help!

Mike



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BushogPapa

07-25-2005 09:58:15




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 Re: Chevy 250 Cid engine problem.. in reply to Mike Burdick, 07-24-2005 09:14:49  
I would check for intake manifold gasket leaks, and around the carb base with an un-lit propane torch, to see if the engine smoothed out.... On the oil pressure..no guess...was the oil pickup tight and in correct position when you had the pan off..?? I have seen pistons fail in these, but that is not the case in your engine...

Ron..



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dieselade

07-25-2005 04:07:45




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 Re: Chevy 250 Cid engine problem.. in reply to Mike Burdick, 07-24-2005 09:14:49  
I`m glad this thread came up..I have a 1974 292 that runs smooth when cold(I have a manual choke on it), then when it is warm, it starts missing and sounding bad, the 5th and 6th cylinders are not firing even with good spark. but it runs good enough to get around and has decent excelleration. it just has this sputering and missing sound at lower speeds. also, if i pull the choke out, it runs better. almost as if it is not getting enough gas. the filter is ok.

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Bill(Wis)

07-25-2005 16:12:26




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 Re: Chevy 250 Cid engine problem.. in reply to dieselade, 07-25-2005 04:07:45  
Have you considered just removing the pistons, rods,etc from the 5 & 6 holes. A friend of mine did that with his Cadillac. Drove it around for years that way.



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Truetramp

07-25-2005 00:39:41




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 Re: Chevy 250 Cid engine problem.. in reply to Mike Burdick, 07-24-2005 09:14:49  
With a older engine like yours, an the problems you've stated. A easy fix, even if it something else. This will help alot. Drian 1 quart of oil off an replace it with 1 quart of Dextron Mercon automatic transmission fluid. Its a high degerant oil an will clean your lifters an valley area out an break up alot of the slug in your older engines. We've used it for years an have had no bad results from it. Run it for about a week an drain it off an go back to your regular oil.....Rick

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Mike Burdick

07-24-2005 19:23:41




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 Re: Chevy 250 Cid engine problem.. in reply to Mike Burdick, 07-24-2005 09:14:49  
I haven"t taken off the timing gear cover yet...but doesn"t the 250 have a gear connected to a gear on the cam...and not a chain or belt?

Regarless...I could see how this could cause the problems though.

Anyway thanks for all the good advice so far...if anyone has more, Id be delighted to hear from you!!

Mike



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Steve Crum

07-24-2005 15:13:47




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 Re: Chevy 250 Cid engine problem.. in reply to Mike Burdick, 07-24-2005 09:14:49  
We had an old 62 chevy 4WD pick up on the farm that had a 235 engine in it that did just about what you described. Several mechanics worked on it but nobody fixed it. Dad finally got tired of dumping money in it and parked it. A few years later, I put together a hot 235 engine in tech school for the truck and put it in it. Several years later I pulled the timing cover off the old engine and found the cam to be two teeth out of time. The cam gear had 2 teeth side by side that were missing the back half of the teeth. Our conclusion was something had gotten into the gear and broke one tooth which broke the other. This forced the cam out enough to loose oil psi momentarily, and the cam snapped back into position albeit, 2 teeth out of time. Oil psi returned to normal and one of the mechanics apparently thought he solved the 'ignition timing' problem by setting the distributor accordingly.
That engine ran rougher than a cob for obvious reasons, amazing it ran at all. I've never killed a chevy 6, but replaced the 292 in my Grandfather's 66' C-60 stakebody with a 427 and he got better gas mileage.

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buickanddeere

07-24-2005 15:07:03




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 Re: Chevy 250 Cid engine problem.. in reply to Mike Burdick, 07-24-2005 09:14:49  
I've seen high mile 230/250 engines jump a tooth retarded on the timing chain.Tends to happen if somebody is horsing around. If the engine is running cold, that is less than 195F. The fuel will puddle in the intake manifold and ports. The hot air stove that feeds hot air from around the exhaust manifold into the aircleaner has to be working. Cold air won't vaporize the fuel into vapour so it can burn, like hot intake air will.

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mike1111

07-24-2005 14:22:55




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 Re: Chevy 250 Cid engine problem.. in reply to Mike Burdick, 07-24-2005 09:14:49  
try spraying some carb cleaner or wd-40 around the base of the carb. the base gasket could be shot. if the rpm"s pickup while spraying thats your problem, don"t know why you lost the oil pressure. let everyone what you find is the problem,, good luck mike



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CRUSADER

07-24-2005 14:08:13




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 Re: Chevy 250 Cid engine problem.. in reply to Mike Burdick, 07-24-2005 09:14:49  
I had a 75 Chev 1/2 ton pickup with the 250 6 cylinder in it. It started doing something very simular to what you describe what yours is doing except it didn't have the serious drop in oil pressure. After changing the fuel pump for the second time, I realized that the hoses on the fuel line were dry rotted and allowing air into the system thus keeping it from pumping the proper amount of fuel to the carburator to run. After replacing all the rubber hoses on the fuel line I never had another problem with it running bad and trying to starve out or die. You may want to give the fuel lines an inspection. Don't know if this is the problem but it might be worth looking into. That old truck is still sitting in the pasture and has had some parts robbed off of it to keep a few other vehicles that were needed to be kept going. I am sure that if I put it back together that it would still run good and get about 17 miles to the gallon of gasoline like it used to.

Hope this will be of some help.
Jim

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Bill(Wis)

07-24-2005 13:31:41




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 Re: Chevy 250 Cid engine problem.. in reply to Mike Burdick, 07-24-2005 09:14:49  
All of the things pointed out below happen to the 250 and more. Lots more. I had two of them. They were the worst engines ever for running rough but you couldn't kill them. One day I discovered the two nuts that hold the carb on were loose (finger loose). GM didn't believe in lock washers. I tightened them down and thought that was the problem, but, it only helped a little. Each time something seemed amiss and a repair was made it would help a little - maybe. Rough running was just something I lived with for the 400+K I drove those engines. Never again.

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Coloken

07-24-2005 13:47:21




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 agreed.. in reply to Bill(Wis), 07-24-2005 13:31:41  
Bill, I think the biggest thing wrong was the manafold/carburator. I tried every thing to tune up mine but 13 MPG was it. Worst carburator ever made. Yes, I could duplicate Mike's problem any time I wanted. All I had to do was get stuck in snow or mud, get mad and race the engine. Eventually, it would pick up the lifters and return to normal.
Kennyp



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petetx

07-24-2005 13:12:33




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 Re: Chevy 250 Cid engine problem.. in reply to Mike Burdick, 07-24-2005 09:14:49  
keeping rislone with each oil change usually stops lifter problems also replace the rotor some times they look good but still don't get the job done these years GM problems had that problem



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Coloken

07-24-2005 11:38:35




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 Re: Chevy 250 Cid engine problem.. in reply to Mike Burdick, 07-24-2005 09:14:49  
If it is like the 230 I had....Every now and then I woild have the lifters collapse. Like if I was stuck in mud and over reved the engine. Would take some time for it to smooth back out. I think it was caused by the oil pump picking up air. First time I did it, though I'd blown the engine. Ran it for years though. Soumds like same thing...low oil or pump pickup bouncing up?
Kennyp



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1966ChevyC-10

07-24-2005 11:29:52




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 Re: Chevy 250 Cid engine problem.. in reply to Mike Burdick, 07-24-2005 09:14:49  
Mine had the same problem. All it was, the distributor bushings had worn out causing this problem. I was later told that the 250s were notorious for wearing out distributor bushings, letting the point gap vary while it is running, causings it to run rough.

1966 Chevy C-10



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Mike Burdick

07-24-2005 12:39:11




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 Re: Chevy 250 Cid engine problem.. in reply to 1966ChevyC-10, 07-24-2005 11:29:52  
My engine has an electronic ignition system and it looks fine. Good thought though.

When the engine was running it sounded like something rubbing but couldn’t pinpoint the source. My first impression was that is was coming from the carburetor area.

A couple of other facts:

The oil indicator is a pressure type from the engine – not electric.
Before I removed the pan I drained the oil. I ran a magnet thru it and found no metal or filings. When I removed the pan there wasn"t any broken pieces of metal in it.
Took compression test and all cylinders were within specification and all readings were close to each other within a few psi.
From the bottom the cylinder walls feel smooth (what I could see of them) and the engine has not used any oil.

The truck is only used around the ranch so it has only 36,529 miles on it and the engine. Everything was in good working condition and I change the oil and filter on it every 2,000 miles plus or minus a few.

I can understand something going wrong in the ignition system or the carburetion but with it combined with the oil pressure dropping – this has really got me baffled!

Any and all help and suggestion are sure welcome.

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Leland

07-24-2005 11:15:50




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 Re: Chevy 250 Cid engine problem.. in reply to Mike Burdick, 07-24-2005 09:14:49  
Look at plugs , wires +cap and rotar this could be the reason for running rough



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old

07-24-2005 10:42:53




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 Re: Chevy 250 Cid engine problem.. in reply to Mike Burdick, 07-24-2005 09:14:49  
Have you checked the fuel filter?? I'd also change the oil and filter and look at the oil close for metal in the oil. Those old 250s are almost bullet proof. Shoot I have 4 or 5 of them laying around in my shop. One even has a complete rebuild on it with only 3000 miles. Bored 40 over cammed etc. Only reason its in the shop instead of being in the truck is that the frame broke on the truck so I pulled the engine. I'd also do a full tune up with cap and rotor seen more then once a cap just go south with out any warning

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Loren

07-24-2005 09:22:37




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 Re: Chevy 250 Cid engine problem.. in reply to Mike Burdick, 07-24-2005 09:14:49  
First thing that I thought of is to check the oil level. If the pressure dropped it may be due to low oil, which can also cause the lifters to collapse, changing the running quite a bit. Usually the lifters will not pump back up until run for a while with good oil so that says this isn't the problem though. ???



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Mike Burdick

07-24-2005 09:35:15




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 Re: Chevy 250 Cid engine problem.. in reply to Loren, 07-24-2005 09:22:37  
Loren,

Like you, I suspected the oil level the first thing. It was okay. But you bring up a good point about the lifters…could one of those be a problem?

Mike



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Loren

07-24-2005 10:21:37




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 I'd really think not.. in reply to Mike Burdick, 07-24-2005 09:35:15  
I haven't ever seen or even heard of a lifter causing problems then "fixing" itself to this extent. I've seena lot of them that won't hold pressure enough that they are running on basically a 0 lash setting(ticking off and on). But haven't seen them collapse enough to cause a problem then come back. Have you changed the oil filter lately? Saw one instance where something in the new filter blocked the oil, dropped pressure and made the fella change his shorts. Was there any noise associated with the pressure drop and is it a mechanical guage or electrical? Maybe a electrical short problem, oil was fine but read wrong, short caused a ignition problem?

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