Anytime you find cylinders with low compression, the next thing that is done is a leak-down test on those cylinders.
Tester
What about the timing being way off?
That has absolutely nothing to do with low compression.
Tester
I realize that. I was asking what on earth would.make the timing so off.
A worn timing chain?
Tester
Worn or skipped? The engine was running fine and then bam it was not. It seems like the chain skipped to me but what the hell do I know thatās why Iām asking you guys. I just donāt want to tear into it if thatās not the problem. Thanks for your kindly advice
As I mentioned earlier, maybe the problem-prone TFI module has failed and it has lost the SPOUT signal.
With no SPOUT the timing will not advance properly. Again, this goes back to checking for DTCs.
A timing light could be connected, the engine allowed to idle, and the SPOUT disconnected. You should see the timing mark move considerably.
And yes, itās possible the timing chain could have jumped suddenly. Timing chain slop can be checked without taking much of anything apart.
If a timing light is connected you could also watch the timing mark on the balancer and note if itās dancing around; another sign of a worn chain.
FWIW my experience with Ford push rod engines goes back a few decades and when they jump time compression will drop significantly in my experience. The compression numbers you posted earlier do not indicate jumped time though. And if the chain jumped indexing the plug wires clockwise 1 position will advance the spark and often enable the engine to run somewhat better.
Someone back here mentioned the cap and rotor and a crack/carbon track can result in cross firing of a cylinder resulting in missfire and backfire.
@Tester, I missunderstood this post. No, certainly late ignition timing has no effect on compression
.[quote=āTester, post:43, topic:100684, full:trueā]
That has absolutely nothing to do with low compression.
Tester
[/quote]
What do I know? But I was stopped at a stop light with the engine at idle and the engine stalled. No warning nothing. Put a new gear and chain on and it was fine for another 100K. Thatās the way it happens sometimes.
Just out of the blue they suddenly wonāt start is the usual complaint. Whether itās a cold start, hot re-start, died at a stop light or coasting to a stop. The Winsor V-8 chains would rarely last 100,000 miles on a pickup with manual transmission on a farm and about 150,000 was tops with an automatic transmission for most drivers. I saw a well maintained Crown Vic with mostly highway miles reach nearly 300,000 before jumping. The owners son worked for me.I liked his work.
Itās a little unclear to me what the OP was looking at with their timing light experiment described above. But if the harmonic balancer timing mark is an inch off from where it should be for the number one spark plug at idle, yes, that seems like it would be a problem that needs to be addressed before perusing other possibilities. I donāt think a loose or jumped timing chain ā while that remains a possibility here ā I donāt think that would have any affect the timing mark alignment on the harmonic balancer for testing the ignition timing, right?
Usually the harmonic balancer is marked off in degrees, not inches. OP, see if you can figure out how many degrees the timing is off, and in which direction. Idle timing on my own Ford truck is 6 deg btdc for example. What is it on yours?
I think he figured the circumference in inches and then divided that by the 360 degrees to come up with the 9 degrees or so per inch. I donāt know if thatās the proper way or not or what works.
Allright I guess I need to sum up what I have said in multiple posts to clean up an clarify this thread.
A friend borrowed my 87 f150 302 drove around the block and called saying it was broke. The engine had lost all power and was making a popping sound when it accelerated(which it would not do) that caused the air filter box to jump. It also will not idle without holding down the peddle.
I checked the compression 2 cylinders where lower # 2 and # 6 at 125 the rest in the 150 range with a cold engine. All cylinders had an initial psi of 100 except for 2 and 6 which were 75.
I did a rotation test on the harmonic balancer to check for timing chain wear and this showed 9 degrees of slop. The test as explained to me was crank it clockwise ti tighten chain then mark the balancer crank counter until rotor moves and mark the difference divide into circumference.
And finally I checked the timing with a light and spout unhooked and it was showing about 20 degrees retarded( at least I think if the mark is past the indicator that would mean retarded). According to Haynes the timing is 10 degrees btdc.
So what would cause this sudden shift in timing? With the spout disconnected is this not a purely mechanical process when it comes to advance/retarding the timing( electronic adv disabled)?
You guys are very kind to help
ignition module ignition module ignition moduleā¦
you can have them tested, but sometimes they will test good ā¦ and badā¦ and good again.
if it isn t a timing problem, or a water in the carb or fuel problemā¦
I would definitely check the ignition moduleā¦
I grabbed a cheap icm on the way home from work and swapped it out. No change so I figured I would set the timing while I was at it. This made it run better as you would expect and now it will accelerate but it is still popping out the intake more forcefully than before setting the timing and it still will not idle. If this gives anyone any ideas please share them.
Thanks
wellā¦ I m sorry if I cost you moneyā¦
is there any chance that you got your spark plug wires switched?
I just clean it up good and return it no worries. Thereās no way the plug wires got crossed. Thanks
Puffing back through the air cleaner will occur if the fuel mix is too lean. You didnāt by chance put E85 in the tank, did you?
No way on the 85 Iām not even sure you can buy that here. Plus I canāt imagine how that would change the timing.