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post #1 of (permalink) Old 12-07-2001, 07:49 PM Thread Starter
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Need Help

I am getting ready to install a Howell fuel injection on my 86cj7 258. Before I do this I need to figure out if my engine is OK. It likes to blow blue smoke at stop lights, sometime a whole bunch sometimes a little. The engine is supposed to have only 10K miles on it. The number 1,2,3,6 plugs are a tan whiteish color and the 4 and 5 plugs are black. I did a compression test

DRY = 1-185 2-190 3-185 4-175 5-175 6-180
WET = 1-195 2-200 3-195 4-195 5-185 6-195

Does this tell me anything? What do I do next?

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post #2 of (permalink) Old 12-07-2001, 08:15 PM
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Re: Need Help

Compression tests can be deceiving. They tell you that the cylinder can hold pressure, and how much. However there's the rub. Because it holds pressure often one thinks that blow-by can't be a problem. When the rings fail to seal, or have been installed wrong ( wrong ring in the wrong postion, upside down, gaps matching vertically, wrong part, gapped wrong, etc...) then you've got to find out what the real truth is... As the pressure builds up in the cylinder it's still leaking out into the crankcase and there's lots of oil being shoved into the cylinder to be burned.

My concern is the blowing of blue smoke while under load. That's classic signs of a ring problem. When you look at the two plugs 4 & 5 and see oil deposits on them... then you know something's wrong. Make sure it's not unburn fuel. The difference is that unburnt fuel will be more powdery, while oil will have the constancy and feel of oil.

If aftermarket fuel injection has one failure it is that if you put it on an engine that's marginal... the problem will be magnified. I've helped several Jeepers install the Howell system and when all's said and done... some were not pleased because of defects in the engine. To many, fuel injection adds another layer of complexity. When you have a problem in an engine and lay EFI ontop of it... it's often difficult to say just were the problem really is.

Were the engine mine... 10,000 miles or not, knowing what I do about EFI, I'd elect to do the job right and have the engine looked at now before you make the situtation more complicated.

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post #3 of (permalink) Old 12-07-2001, 08:38 PM Thread Starter
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Re: Need Help

I agree. I do not want to put the fuel injection on until I am sure the rest of the engine is OK. When you say have it looked at, does that mean take it apart or have a mechanic do some tests on it?

I am not sure that it is smoking under load, when I sit at a stoplight for a several seconds it starts to smoke and sometimes it lets out a big cloud. When I rev up the engine it tends to clear up. No smoke is noticeable from the driver seat when moving. It doesn't smoke much when the engine is cold, the higher the engine temp the more smoke it makes.


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post #4 of (permalink) Old 12-07-2001, 11:26 PM
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Re: Need Help

The choice of taking it to a mechanic or tearing it down yourself is only one you can make. I don't know your expertese level, what tools or manuals you have. IMHO, it's best to take it to a mechanist and have him tear it down and do a rebuild if you're concerened.

From the description you're giving... it almost seems like it's not blowing oil (blue smoke) but it's blowing raw unburned fuel (black smoke). Are you sure it's oil that's blowing out? Is the engine running too rich?

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post #5 of (permalink) Old 12-08-2001, 09:49 AM Thread Starter
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Re: Need Help

I thought it might be fuel at first. What steered me to thinking oil is there is alot of blow by, oil in the air filter. I guess a good mechanic could tell if it is oil or fuel. Would it be normal for just two plugs to be black if it is fuel?

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post #6 of (permalink) Old 12-08-2001, 02:05 PM
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Re: Need Help

If it's running rich the unburnt fuel will be black in color. The tailpipe will also have a sooty deposit in it. If it's oil... you'll really know the difference. If you wipe some of the deposit between your fingers the sooty material will be dry, not wet, and not have an oily feel. Oil will feel just like oil.

It would be normal for the plugs to be black IF the plugs were not firing, or were not able to combust all the fuel.

Here's what Oil fouled plugs look like:



Here's what a plug looks like that's running too rich:




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post #7 of (permalink) Old 12-08-2001, 05:51 PM Thread Starter
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Re: Need Help

OK, I think we may be getting closer to figuring out the problem. There is block soot built up in the tail pipe. Plugs 4 and 5 look like they have been running rich, more so on plug 5. All six of the plugs seem to have oil on the threads, could this be from the valve cover leaking? If the problem is unburnt fuel and not oil how come the smoke is whiteish not black?

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