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Engine starting problem
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Lee Kolb
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PostPosted: Wed Sep 21, 2016 6:20 pm    Post subject: Engine starting problem Reply with quote

I recently pulled my stock 1500 engine to replace the intake manifold. (I could have done it in place, but wanted to check the crankcase bolts and examine the heat exchangers, too.)

The car had been starting and running well, although it started getting noisy last month.

Since I got the engine back in, the car starts but will not keep running for more than 5 or 10 seconds. It will not restart until it has sat for 10 or 15 minutes, and then it runs for an even shorter time.

I thought it was probably a fuel supply problem, possibly some crud dislodged from removing and reinstalling the fuel line. I replaced the inline fuel filter and checked the output of the fuel pump. It seemed normal.

I next checked the level in the float bowl. It was correct.

Then I removed the carburetor (which I had cleaned last July) and recleaned all of the orifices. Put it back with new gaskets.

It still won't run for more that several seconds. Right now, I'm out of ideas. Any suggestions?
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langsmer
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PostPosted: Wed Sep 21, 2016 6:47 pm    Post subject: Re: Engine starting problem Reply with quote

What do you mean by it was getting noisy? Was the engine missing or not running smoothly, or was it knocking or something along those lines? Have you checked if you are getting good spark?
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PostPosted: Wed Sep 21, 2016 8:42 pm    Post subject: Re: Engine starting problem Reply with quote

I would think that if it was starting and running fine before the removal and now not, that it would be something related to the removal.
Sometimes if a carb is tipped the crap that was happy just sitting in the bottom of the bowl doing nothing, becomes a problem.

I would open up the top of the carb and have a look and see what lurks beneath.

gordo.
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Lee Kolb
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PostPosted: Thu Sep 22, 2016 4:54 am    Post subject: Re: Engine starting problem Reply with quote

The car was running very well, and the noise was typical of an exhaust system leak. Right now I want to get the engine working again, and then I'll return to that problem.

I agree that the starting problem must be related to the carburetor removal. I not only took off the top and examined the float bowl, I removed and cleaned the entire unit. It didn't help
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PostPosted: Thu Sep 22, 2016 7:45 am    Post subject: Re: Engine starting problem Reply with quote

I think the title of your thread should really be, engine running problem because it does start--it just refuses to continue to run. Minor point, but the fact it starts tells us that it is getting some fuel as well as spark.

If I remember correctly from your other thread, you added a spacer between the carb and manifold. The fact that the engine will not run for more than a few seconds indicates, to me, that if it is fuel related, the problem has to do with jetting and/or vacuum as that is how a carb works--pulling fuel through the jets via vacuum down the throat.

You have thoroughly cleaned the carb and, we assume, all jets and drillings are clear. You must be certain that the proper gasket was used in the rebuild and the holes in the gasket align with the holes in the carb body. Beyond that, the only change is the spacer on the manifold. You might try removing the spacer and get the set up back to where it was before. See if the engine now runs. If it does, perhaps the spacer was forcing the throttle plate to complete closure or interfering with the direct flow of atomized fuel into the intake. If there is no change, then at least you know the spacer is not the issue.

You also mention you "replaced the intake manifold." If that's the case, it's possible there is a major air leak at the manifold to head gaskets causing an overly lean mixture that prevents the engine from running. You can duct tape a vacuum cleaner hose to the carb, reverse the vacuum cleaner so it blows air, and use a soap solution to find any air leaks.
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Lee Kolb
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PostPosted: Thu Sep 22, 2016 10:59 am    Post subject: Re: Engine starting problem Reply with quote

There is no spacer between the carburetor and the intake manifold Ė you must be thinking of a different thread. And the gasket between upper and lower carb sections I am sure is correctly aligned and sealed. Iíve used a light and mirror to examine the throat of the carb while operating the throttle and choke, and canít see any problems.
I began convinced that my problem was fuel starvation, but now Iím ready to look elsewhere, particularly at the intake manifold, since it was the only change made. The new unit is from Empi, and had two inlet tubes welded on just below the carburetor. Having nothing to connect to these, I closed them off with epoxy, but I think it much more likely that there is a leak there than at the cylinder head connection. Iím ready to try your leak test. Do I have to rotate the engine to close the valves in order for the leak test to work?
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Lee Kolb
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PostPosted: Thu Sep 22, 2016 12:46 pm    Post subject: Re: Engine starting problem Reply with quote

I just ran the recommended leak test on the intake manifold, and found no leaks except a few bubbles at the throttle shaft, which told me that the test was working.

I can understand how an intake manifold leak could cause the engine to die after starting, but have no explanation for why it then won't restart until it sits for a while. That get me back to thinking its a fuel issue.
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PostPosted: Thu Sep 22, 2016 6:02 pm    Post subject: Re: Engine starting problem Reply with quote

Yeah, I probably got you mixed up with another thread.

The manifold leak, if it was massive, could lean out a mixture enough that running would be difficult, but you've eliminated that possibility with your test.

As I reread your posts, I now see that it starts, dies, then doesn't start until it sits for a while. It does seem like a fuel issue but you might as well try a different approach. Next time you get the no start condition, try your test for spark. This is the next logical cause. If you get a strong spark when cranking, you know that's not the problem. If the spark is absent, you may have a bad coil or other ignition issue.
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Lee Kolb
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PostPosted: Thu Sep 22, 2016 7:06 pm    Post subject: Re: Engine starting problem Reply with quote

I'll check the spark tomorrow, but just to clarify--
the problem occurs every time I try to start the car. It is not intermittant. It has never run for more than ten seconds since I put the engine back in after the intake manifold installation.
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PostPosted: Fri Sep 23, 2016 9:47 am    Post subject: Re: Engine starting problem Reply with quote

Lee Kolb wrote:
I'll check the spark tomorrow, but just to clarify--
the problem occurs every time I try to start the car. It is not intermittant. It has never run for more than ten seconds since I put the engine back in after the intake manifold installation.

When it does run for a few seconds is it real raw gassy smelling at the exhaust? When you try to restart it is it real raw gassy smelling at the exhaust?

Both these questions again but; is there zero gassy smell at the exhaust?
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PostPosted: Fri Sep 23, 2016 1:42 pm    Post subject: Re: Engine starting problem Reply with quote

Did you install the intake manifold gaskets when you replaced the intake?
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Lee Kolb
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PostPosted: Fri Sep 23, 2016 4:53 pm    Post subject: Re: Engine starting problem Reply with quote

The spark looked good both from the coil and at the plugs, Nice white arc.

Today for the first time, the car would not start at all, so I could not check for gasoline odor at the pipes. I'm working indors and have started the car many times in the past week, and do not recall any fuel odor.

Definitely new intake manifold gaskets at all 4 locations, and did dig out the old gaskets at the cylinder head before putting in the new ones.

I tore th carburetor down again today to try to confirm that all of the passages are clear. Soaked in in carburetor cleaner again and blew everything out with compressed air. I honestly do now know where all of the passages are, and which ones might be causing my problem.
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PostPosted: Sat Sep 24, 2016 6:43 pm    Post subject: Re: Engine starting problem Reply with quote

Lee Kolb wrote:
Today for the first time, the car would not start at all, so I could not check for gasoline odor at the pipes.

But it still rotated right? If so, and you didn't smell gas then you are not getting gas into the carb.

Lee Kolb wrote:
I'm working indors and have started the car many times in the past week, and do not recall any fuel odor.

Another verification that no gas is getting to the carb. Have you removed the needle and seat, cleaned, and blown through it to see if it's open.
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Lee Kolb
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PostPosted: Wed Sep 28, 2016 5:57 pm    Post subject: Re: Engine starting problem Reply with quote

Just wanted to let you know that I haven't given up.

I am now confident the carburetor is OK. I found a shop manual that described how it works, and carefully checked each jet and passage. They were all clear.

When I put it back on, the car again started, ran briefly, and died. After some fooling around, I discovered it would continue to run if I clamped the choke partially closed. That is, I could keep the engine going as long as I kept tapping the accelerator. At this point, I know that it isn't blockage in the fuel path.

Now I'm really suspecting the new intake manifold, so I pulled the carburetor again and took a closer look at the manifold. I found that the inlet is very rough, with a lot of weld protruding into the air passage, and the end of the auxiliary inlets also protrude. I am having the hole in the heater passage of the old manifold welded up and will reinstall it next. Perhaps the new manifold doesn't provide enough vacuum to pull the fuel through the carburetor.
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PostPosted: Wed Sep 28, 2016 6:22 pm    Post subject: Re: Engine starting problem Reply with quote

You have adjusted your valve clearances, right? And , set your timing (static) first?
So, good spark when cranking after dies.
Can keep running with choke or dance on throttle.

Still seems like it is not getting gas through the idle circuit. When you step on the throttle you are feeding gas through the accelerator circuit, and when you choke it you feeding more through the mains.

What happens if you crank the idle mixture screw out a few turns?

gordo.
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Lee Kolb
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PostPosted: Thu Sep 29, 2016 4:06 am    Post subject: Re: Engine starting problem Reply with quote

I'll let you know after I get the manifold swapped and the engine back in the car.
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PostPosted: Thu Sep 29, 2016 6:07 am    Post subject: Re: Engine starting problem Reply with quote

Out of curiosity, did you check/verify the "anti-diesel/fuel shut off" solenoid on the carb is not sticking closed? The coil has a tendency to get weak over time and causes the fuel flow to get stopped, or the plunger will get stuck, etc. Just a thought.
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Lee Kolb
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PostPosted: Mon Oct 03, 2016 2:37 pm    Post subject: Re: Engine starting problem Reply with quote

Problem solved. I finally got the old intake manifold installed and the engine back in, and it started immediately and ran normally. The new manifold was somewhat restricted and bumpy just below the carburetor mount, and it must have affected air flow and the pressure reduction in the carb throat. Not a great purchase.

This is an early 30PICT-1, and does not have a fuel cut-off. I think I removed it and plugged it years ago when I purchased the carb.
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PostPosted: Tue Oct 25, 2016 6:19 pm    Post subject: Re: Engine starting problem Reply with quote

Here are a couple of photos of the new Empi intake manifold that my engine didn't care for. I suspect that the air flow through the carburator was disturbed enough that it didn't draw fuel properly.
Image may have been reduced in size. Click image to view fullscreen.

Image may have been reduced in size. Click image to view fullscreen.

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PostPosted: Tue Oct 25, 2016 7:22 pm    Post subject: Re: Engine starting problem Reply with quote

Show more pictures of the rest of the manifold. It looks as though the intake runner below the upright section has a crack (painted over).

Gordo.
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