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Old 04-14-2013, 03:01 PM
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Why would cylinder not fire (5.0)?

I installed a remanufactured 5.0 with abour 15,000 since the rebuild. When I changed the pan, I check the bearings and cylinders. Everything was in good shape so I cleaned it, painted it and installed it.

It fired right up and seemed fine until I drove it. I could tell there was a skip. After messing with it, I noticed that when I pulled the plug wires for 3 and 8 there was no change in RPM. I did a compression test. All the cylinders were at abour 150 except #8. It was at 0 PSI. I pulled the head and found that the intake valve lookes rough. It didnt match the others and looked almost like it was rusted.

The #3 cylinder has 150 PSI but didn't seem to fire. Could this have anything to due with the #8 intake valve not sealing?

Why would it not fire if it has good compression and spark? I have not pulled that head yet. Plan to do it tonight.

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Old 04-14-2013, 05:18 PM
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I take it from your previous posts that it's a 302 Ford? Is that why you replaced the balancer earlier this year? It could be a number of things that could cause this, but, what is the engine in, what year of Ford 5 liter is it. Is it controlled by and ICM or distributor. I take it that you had spark for cylinders #3 and #8? Is it fuel injection or are you running a Carb?

Ray
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Old 04-14-2013, 07:14 PM
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3 and 8 are on the same intake runner. reversion from the number 8 intake valve leaking is messing with the intake charge for number 3 cylinder
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Old 04-14-2013, 07:28 PM
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It's a 92 5.0 from an f250. I t was remanufactured by Jasper engines and installed in 07. I removed all of the EFI equipment and installed a Wieland intake and Edelbrock 1405 carb.

I just came in from pulling the opposite head. All of the valves look good on that head.
The one valve that is bad is smaller than all the others. It looks like they skipped it during the rebuild.

LATECH confirmed what I was expecting.
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