Low compression on cylinder 1, 50psi, less than 10hr on new crate motor

[firebird1158]

The new motor is a 305 gm crate and has been smelling rich and smoking lately,had some gas in the oil as well.put vacuum gauge on and it was flickering at 15 at 1000 rpm.Well just finished a compression test and number 1 cylinder had 50 psi where as all others had 185-190 psi. I poured a little oil in the cylinder and got a reading of 55 psi. So does that mean I have a bad valve?? I took off the valve cover and the springs look ok, not really sure what to look for??? As with original issue it stinks rich of fuel and smokes out the exhaust. Should I pull the head? Don't have a leak down tester.

 

[ondarvr]

Wouldn't a crate motor have a warranty? I wouldn't touch it until you pursue a warranty claim.

 

[Scott Danforth]

As with original issue it stinks rich of fuel and smokes out the exhaust.

my guess is your fuel system needs attention. whatever killed your first motor has probably now killed your second motor. if you paid someone to do the swap, you can get warranty.

if you did the work yourself, you may be denied warranty.

I wouldnt pull anything apart until you check on warranty.

you could in the mean time, get a borescope and look in thru the spark plug hole. Amazon has a nice one for a bit over $100 with a small 5mm diameter camera.

is this a fuel injected motor? Carbed motor?

if fuel injected, I would look for a leaking injector dumping fuel.

if carbed, I would be looking at spray patterns.

Have you also checked for spark?

 

[firebird1158]

It is a crate motor but minute it hits the water, no warranty gm told me, I did pay for swap,switched head gaskets and put marine cam in it... they did say get someone to work on it and they will try to get it covered. It is a TBI setup and had already swapped injectors and pressure regulator rebuild. I am thinking valve issue but will need to remove head I think....

 

[dypcdiver]

Find some way to pressurise the cylinder with air at TDC on the firing stroke, get a fitting that "T" 's into your compression tester or something like. If you don't have access to a compressor then a connection to a spare tyre would do. 30 psi would be plenty, then remove the flame arrestor and listen for leaks at the TBI if no sound then pull the Riser and listen at the manifold. this would confirm a valve leak.

I still think you will need to pull the head though.

 

[jerryjerry05]

Sounds like a bad valve.
Sounds like you voided any warranties so go ahead and pull the head.

 

[Grub54891]

Google leakdown tester.

 

[Scott Danforth]

my compression tester works as a leakdown tester as well (I just need to remove the schroeder valve)

 

[firebird1158]

No Title

Well , I pulled the head and still have no idea what is wrong.... the valves in cylinder one look good, cylinder looks ok, no scratches, still see crosshatching, head gasket doesn't show any obvious signs of leaking.... going to bring to head shop tomorrow to have checked. have a look at the pics and see if anything jumps out at you guys, thanks for the help, its greatly appreciated

 

[firebird1158]

No Title

Here are a couple more....

 

[dypcdiver]

Are you sure that is a new motor there seems to be a lot of corrosion around. Having said that No.1 looks as if it has been washed out by either too much fuel, water or not even firing, are you sure the spark plug was good?

 

[firebird1158]

Are you sure that is a new motor there seems to be a lot of corrosion around. Having said that No.1

looks as if it has been washed out by either too much fuel, water or not even firing, are you sure the spark plug was good?

Does washed out mean the rings are bad? Not sure what problem was, vacuum was shakey at 15 , sprayed carb fluid for vacuum leak, nothing. Had changed plugs, rotor and cap

Would not firing for too long ruin the rings? It would still be getting oil??

 

[firebird1158]

Well just got off phone with head shop and I had "sucked up a valve" from getting too hot they said... issue has been too much fuel I thought, not lean,either way i have replaced injectors and rebuilt pressure regulator, and now have an answer to why my compression was so low.... still wondering if the washed cylinder is going to give me trouble as well.. hopefully not, will put some transmission fluid in there to help

 

[firebird1158]

So this was end of last season, so now that everything is back together, I have all cylinders at 185 psi but low vacuum and running so rich that I am growing oil with fuel in it. Removed 7 liters , been keeping a close eye on it. What could cause this? Maybe the intake didn't seal properly? Sprayed carb cleaner around intake with no idle difference as well as propane. Checked coolant temp sensor and jumped it, seems to be working as it cut spray back. Thanks for any help.

 

[Scott Danforth]

Failed spark on one cylinder?

 

[firebird1158]

Failed spark on one cylinder?

I put all new plugs when I just redid compression test but have a wire tester, will test them all tomorrow to be 100%