3 Cylinder Engine?

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ITA124
Posts: 128
Joined: Wed Nov 12, 2008 1:51 am
Your car is a: 1976 Fiat 124 Spider
Location: Sydney, Australia

3 Cylinder Engine?

Post by ITA124 »

Hi Guys,

I'm stumped and asking for suggestions. My engine is not running on #1 cylinder. With the car idling or at moderate revs, I pull the spark plug lead and there is no change in the engine. With an infrared gun, the exhaust temp is below 100 deg.

So far I have done the following;

Ignition
1. Replaced the entire system. Coil, Module, Leads, Plugs. Even put a rebuild kit through the dizzy. Spark looks great. With the lead off the cap, it jumps over 1 1/2"
2. Pulled #1 lead and connect to a spare plug. Firing nicely across gap

Fuel
1. Put had over trumped at idle. Found fuel running out trumpet. So there are hydrocarbons in there.
2. Pulled inspection cover off DCOE and removed all screwed in items and used an air gun to clean fuel circuits. Swapped jets around.

Engine,
Compression test
1 = 125psi
2 = 100psi
3 = 80psi :shock:
4 = 100psi

On the road
1. Rev the sh!t out of it. Sounds very fluffy. Goes OK? at best
2. At speed and off throttle, the exhaust farts and back fires
3. When I turn engine off, there is a pop from the exhaust

Cheers,
Paul
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azruss
Posts: 3659
Joined: Sun May 30, 2010 12:24 pm
Your car is a: 80 Fiat 2000 FI

Re: 3 Cylinder Engine?

Post by azruss »

from what i gather, you are running a single carb. It sounds like your spark is sorted out, so you have a fuel issue. I would start by looking for leak in the #1 intake manifold tube. If you are sucking air, the mix may be too lean in #1 to fire. This could also cause the popping and backfire . If I was a betting man, i would put money on a bad intake manifold gasket.
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User avatar
ITA124
Posts: 128
Joined: Wed Nov 12, 2008 1:51 am
Your car is a: 1976 Fiat 124 Spider
Location: Sydney, Australia

Re: 3 Cylinder Engine?

Post by ITA124 »

I'm running twin 45 DCOEs

I have a plan of attack for today and one point is manifold leaks. So we're on the same page.

Cheers,
Paul
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majicwrench

Re: 3 Cylinder Engine?

Post by majicwrench »

INtake leak would have to be huge to affect it on road. Take hunk of vacuum hose and listena round runner.
Certainly possible to flood one cylinder. How does plug look??

When did all this start?? Compression does not neccessarally reflect good valve opening/closing. IN other words, your compressin can be OK, but a valve may or may not be doing the right thing.

Might do a running compression test. On #1 and a known good cylinder.
Keith
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