Low compression on 1, 3 and 5

[Quickstop [UK]]

Been working on a friend's truck (MDH and his Syclone) this weekend.Truck has been getting really poor mileage so we checked the plugs. 1 was filthy so we thought maybe a sticking injector and cleaned it.

We took the #1 lead off and had good spark. Took the plug out and it was filthy black, no oil and held it to ground and had a good spark. Without the #1, there was no difference to idle. If we took another lead off though, it was very rough.

We thought that 5 cyl is manageable with the high idle but that 4 cyl was too little. Seemed like #1 was making no contribution to power.

Spark was good so to be thorough, we checked comp and got about 40 psi. #3 had similar and also had a blackened plug. #5 had a Pretty clean plug and 120 psi.

The truck runs, idles high and is bad on mileage but we're wondering if we missed something before we take the head off. We'll compare 2,4 and 6 today and try and get a leakdown test as well but from the indications so far, what do you guys think?

I thought maybe a valve was badly done as the truck had a receipt for a valve adjustment a while back but we set it at TDC on 1 using the rockers moving/ lash method and still got low comp.

Took the rocker nuts off and got a similar result so I think the lash settings were ok.

What do you guys think?

 

[Ty#0318]

Re: Low compression on 1, 3 and 5

I have the same with mine...
I'm thinking about valves. Checked injectors. Had to buy new ones.
And my FPR was bad.
Had to replace intake manifold too.
I had fuel in engine oil.
Check how Yours smell...

 

[Quickstop [UK]]

Re: Low compression on 1, 3 and 5

Also, no oil in the water, smoke or excessive loss of water.

 

[blacktyaffair]

Re: Low compression on 1, 3 and 5

Could you perform a leak down test and post results?

 

[Quickstop [UK]]

Re: Low compression on 1, 3 and 5

Yeah, leakdown is the next step I guess. Can't believe how well it runs with 4 or 5 cylinders! We took 3 and 1 injectors off the harness and it sounded fine.

Damn.

 

[RealFastV6]

Re: Low compression on 1, 3 and 5

Just a guess looking at what you've got going on, but I think you may have lifted the head here (below) and you've got a blown headgasket.

http://www.syty.net/forums/showthread.php?t=79282&page=4

Either way, tear down forthcoming. Bummer.

 

[Quickstop [UK]]

Re: Low compression on 1, 3 and 5

Just a guess looking at what you've got going on, but I think you may have lifted the head here (below) and you've got a blown headgasket.

http://www.syty.net/forums/showthread.php?t=79282&page=4

Either way, tear down forthcoming. Bummer.

Sorry, should have been more clear. Not my truck.

Yeah, tear down is in the pipeline.

BTW, I have no idea how my truck didn't die with that experience. Had good oil pressure and good compression on it since then. I think 37lbs of boost with 20lbs of fuel wasn't enough to lift the head. I got really lucky.

 

[RealFastV6]

Re: Low compression on 1, 3 and 5

Sorry, should have been more clear. Not my truck.

Yeah, tear down is in the pipeline.

BTW, I have no idea how my truck didn't die with that experience. Had good oil pressure and good compression on it since then. I think 37lbs of boost with 20lbs of fuel wasn't enough to lift the head. I got really lucky.

:rotf:

It's obvious I'm a bit of a "skimmer" when reading long posts huh.

Still sounds like a gasket issue with two cylinders next to eachother both blackened.

 

[MRKING]

Re: Low compression on 1, 3 and 5

Sometimes cleaning the injector tips isnt enough to get a bad injector properly working again . On the suspected bad cylinders , try swapping in a known working injector . You've isolated the problem as far as which cylinders aren't running at 100% , now if they are getting good spark see if you can manipulate the condition by leading the problem to another cylinder . That way you'd know for sure what the problem is .

Injector issues seemed to be the main project at our wrenching meet in january . Swapping parts around may take an extra hour to do , but overall , less money was spent on replacing "still good" parts .HTH .

 

[MRKING]

Re: Low compression on 1, 3 and 5

You also could be a few degrees off on the TDC given the method you described . A piston stop is not expensive , between a few members everyone throwing in a 20 would cover it . Not having TDC set accurately in the long run will cost alot more . If this engine will be getting torn down soon , at least have him pick one up for the rebuild .

 

[Quickstop [UK]]

Re: Low compression on 1, 3 and 5

You also could be a few degrees off on the TDC given the method you described . A piston stop is not expensive , between a few members everyone throwing in a 20 would cover it . Not having TDC set accurately in the long run will cost alot more . If this engine will be getting torn down soon , at least have him pick one up for the rebuild .

Thanks Mike but we went over the timing and the valves about 3 times. TDC was established by watching the intake on #1 move and as it stopped moving and closed, the second line on the balancer came into alignment with the saginaw marker. I'm pretty certain TDC was in the right place. I don't think that it's the valve setting as I set it on my truck the same way and had 160-170 psi when I built my motor.

We saw nothing to indicate that there was a problem with the injector - did a test using a syringe and the battery and it closed/opened correctly.

We're leaning on low compression due to a gasket that's blown through so looking at options to investigate that but it seems like the head has to come off in any case.

Other option is bent valves but seems odd that both 1 and 3 would have the same problem...

 

[MRKING]

Re: Low compression on 1, 3 and 5

I was assuming since you said having the no.1 injector unplugged , and it making no difference in idle condition, that it would mean you have a spark or fueling problem . The spark seemed ok when you checked it so it sounded like the injector may be bad . I was about to go out and do some yard fertilizing earlier when i posted so i may have misread something or wrongly assumed . Let me know what you find out either way .

 

[Quickstop [UK]]

Re: Low compression on 1, 3 and 5

I was assuming since you said having the no.1 injector unplugged , and it making no difference in idle condition, that it would mean you have a spark or fueling problem . The spark seemed ok when you checked it so it sounded like the injector may be bad . I was about to go out and do some yard fertilizing earlier when i posted so i may have misread something or wrongly assumed . Let me know what you find out either way .

Hey man, no worries Did I seem critical? Didn't mean to! Appreciate all input.

It seems like aside from the leakdown test, there's not much to be done other than pull the head so when we figure it out, we'll post up.

It's crying shame as we were hoping to do some tuning on the truck at the track in 2 weeks and by the time we have gaskets from the US, we'll have missed the chance... unless...

:tup:

 

[MRKING]

Re: Low compression on 1, 3 and 5

Yeah no worries here . I want to get my blue turd running real bad as of lately so I've been trying to help out any others in what ways i can .

I'm hoping if i pay it forward enough , my truck will have less problems when its my engine bugs that i'm trying to diagnose . I doubt it will work out like that but at least i get to enjoy the random problem solving . LOL.

 

[RealFastV6]

Re: Low compression on 1, 3 and 5

Yeah no worries here . I want to get my blue turd running real bad as of lately so I've been trying to help out any others in what ways i can .

I'm hoping if i pay it forward enough , my truck will have less problems when its my engine bugs that i'm trying to diagnose . I doubt it will work out like that but at least i get to enjoy the random problem solving . LOL.

Thats right!!! SyTy karma!! :tup:

 

[Quickstop [UK]]

Re: Low compression on 1, 3 and 5

Found the smoking gun:

Rebuild next Saturday when the new gasket arrives.

 

[MRKING]

Re: Low compression on 1, 3 and 5

Justin was right , good call .

You guys going to do more while your in there ? My memory is fuzzy on what the stock pistons look like , is that damage to the side of where the gasket was blown ?

 

[Quickstop [UK]]

Re: Low compression on 1, 3 and 5

No, budget means no upgrades. We talked of doing an L35 swap but that gets expensive fast over here with shipping etc.

I do wonder where the gasket material went though. We'll just have to suck it and see.