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Compression test results


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6 replies to this topic

#1 thedoctor

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Posted 27 January 2005 - 03:44 PM

This is an 83 dl EA81 166K no start in cold, new plugs have black deposit. Started with ether a couple days. This morning that didn't work. In the warm shop... started right up. Compression test in order 1,2,3,4: 165, 145, 190, 185.

I need some help on what to do next. It has a Carter-Weber that I can get a rebuild kit for (from Advanced Auto Parts). I have no experience with that, but life is for learning. Everything but wires have been replaced on the ignition side. Wires were new 18 months ago.

#2 85Sub4WD

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Posted 27 January 2005 - 04:41 PM

I know that "knock off" AKA advance/pepboys/autozone wires are BAD BAD BAD. may be a coil/sparkplug problem? If the rebuild kit is not expensive, it may not be a bad idea to go ahead and rebuild the carb. Beyond that, I don't know.

#3 NoahDL88

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Posted 27 January 2005 - 06:02 PM

How are you numbering your cylinders? Posted Image Cause your compression dosn't seem right, you either have no compression up front or no compression on one side, i'm assuming head gasket on the passenger side. that shouldn't make a difference though for cold starting, look at the cylinders with low compression and see if theres any green on them, could be headgasket. check to make sure that you have your choke connected, and don't forget to mat the throttle to "prime" the engine and start without your foot on the pedal, obvious i know.

From the black it could be oil or gas, the smell should let you know. could be water in the lines... now i'm just reaching for straws

#4 thedoctor

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Posted 27 January 2005 - 07:46 PM

I have my cylinder numbers correct so 1:165, 2:145, 3:190, 4:185... but I don't know how to interpret these numbers. I heard anything over 130 was good on an engine with 166K miles, but what about the difference between the cylinders? Is it significant.

Does fuel pump pressure have anything to do with start up?

#5 85Sub4WD

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Posted 27 January 2005 - 07:52 PM

Fuel pump would not have much to do with startup, but given your miles, you will be replacing one soon anyway, and if it is REALLY acting up I could kinda see it. I seriously doubt a blown headgasket; in all cases I know of the compression was VERY low (under 100psi) and the engine was eating large quantities of oil/coolant/both. I will admit that there is a lot more variation than I would expect, probably worn rings, but nothing fatal. Also if you had compression issues starting would be accompanied by a plume of smoke of some sort. I think a new fuel pump/filters (toss old ones) and a carb rebuild should undoubtedly solve the problem. Also, you should have NO MORE THAN one fuel filter, and that filter should be AFTER the fuel pump, and before the carb. I looked at the Haynes manual's representation of the carb and it did not look bad at all, from the rebuild standpoint, should be very doable for a novice.
Good Luck
P.S. you can check fuel pressure with a fuel pressure gauge to verify that it is the fuel pump.

#6 thedoctor

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Posted 27 January 2005 - 08:23 PM

I have two fuel filters. One in the back next to the fuel pump, and one under the hood (that one has a third line coming straight out the top). A few weeks ago I was having power loss that was greatly improved by replacing the rear filter. The front one is relatively new also.

The carb rebuild kit turns out to be expensive $200 plus from the factory. The Advance folks were talking about a Hitachi kit. I can't lay out that kind of money with knowing what the problem is. If I found a used Hitachi and manifold, that would fit my car right? Then later I could upgrade to a Weber.

$31 for a fuel pump is different.

There must be an answer to why this sucker starts warm but not cold.

I will do a cold compression test and see what that says. I will put on a new fuel pump and another new filter. But I am not getting that Ah Hah! feeling at all.

#7 85Sub4WD

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Posted 27 January 2005 - 08:29 PM

I'm sorry :( , I completely understand. Check with CarQuest, NAPA, and even check with Weber before you rule out a carb rebuild. I got a kit from CarQuest for $30 for my Hitachi. I feel more like it is the carb than the fuel pump, because the carb is supposed to retain fuel in it for startup in the bowl.
Anyway, best luck!




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