The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

Please Support Fuel Injector Clinic
Please Support STM Tuned

1G 1990 GSX failed compresion test

This site may earn a commission from merchant
affiliate links, including eBay, Amazon, and others.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Co-Bolt

Proven Member
34
3
Jan 17, 2013
Mannford, Oklahoma
My 1990 GSX wasn't starting, so I did all I could and then took it to a shop when I gave up. The shop told me that the compression in each cylinder was around 70-73 psi. They were also able to get it started when they put oil on top of the pistons. I need help with a couple things now, I think it may be the piston rings but I'm not entirely sure. What do you guys think?

This is the current state it's in:
You must be logged in to view this image or video.


I also plan on doing the following before I put it all back together:
Re-gasket
New water pump
New timing belt kit
Get the head machined? (Should I? Or is it not really necessary?)

Is there anything else I should do to ensure everything is in good shape? I'm also on a ~$1000 budget here
 
Backup, what were the events leading up to this no start? There are some things we won't know now since ghe head has been removed. I doubt comoression would be that bad from rings alone. What happened when the car was running?
 
70-73 psi on all 4 cylinders?

I doubt rings, if it was one or 2 cylinders, I could go that the engine over heated and you lost tension in the tings.

But all 4? that reads more of a mechanical timing issue., the belt jumped a tooth or two.

At this point I would fluid test the valve seating, and fluid test ring seal in the block.

Who cut the timing belt?
 
What happened when the car was running?

Okay so my car was running just fine, only problem I ever noticed was that something was gradually eating up oil; so I'd top off every week or so. I had been needing to change the oil for a long while, I had new oil purchased and everything but I just never had time. My job had me driving 100+ miles a day so my car was being used a lot. Drove home from work one day just fine then that night it snowed/iced and got extremely cold. Tried to start the car and it would crank and sputter, but it would not start. I just figured it was the cold, so I waited until it got warmer, still no start--tried jumping it and everything. I checked everything else; I've got fuel, spark, air, and my ECU was recently rebuilt. I was stumped so I took it in, shop basically told me compression was low in the chambers and that I need a new engine, and that I need to take it to a performance shop to replace it. I can't really afford it so I decided to do it myself; I have a spare 6 bolt short block in my shed anyway if I need to replace the entire bottom end.

70-73 psi on all 4 cylinders?

I doubt rings, if it was one or 2 cylinders, I could go that the engine over heated and you lost tension in the tings.

But all 4? that reads more of a mechanical timing issue., the belt jumped a tooth or two.

At this point I would fluid test the valve seating, and fluid test ring seal in the block.

Who cut the timing belt?

I'm not entirely sure if it was all 4, the shop wasn't really specific when they called me. As for the timing belt, when I took the top of the timing cover off the timing belt was on pretty secure, didn't look like it jumped time. I cut the timing belt to make it so I can take off my head without having to take off the bottom half of the timing cover; I have a new timing belt kit to replace it anyway.
 
Cars dont go from running fine to 70 psi compression without something failing. My guess is you jumped time. Just because it "looked fine" doesnt mean anything. Since you already took it apart no way to do a leakdown. Id have that head inspected. You may have other issues but I would start there.
 
Cars dont go from running fine to 70 psi compression without something failing. My guess is you jumped time. Just because it "looked fine" doesnt mean anything. Since you already took it apart no way to do a leakdown. Id have that head inspected. You may have other issues but I would start there.

Now are you sure it would be an issue from timing? It was able to start and run for a couple minutes after they put oil on the pistons.
 
I cant be sure of anything. Im making educated guesses based on limited information and 25 years of experience. Youre torn down yhat far, you could go ahead and pull the pistons and have a look. It ran after oil....but how well?
 
I cant be sure of anything. Im making educated guesses based on limited information and 25 years of experience. Youre torn down yhat far, you could go ahead and pull the pistons and have a look. It ran after oil....but how well?

Well enough to drive it around the lot, just with plenty of exhaust smoke from the oil.
 
Are you doing all the work yourself? If not, there's no way you'll get everything you listed done for $1,000.

Here's what I would do; find a long block and do a 1 for 1 swap. In the end, it will take less work and probably be cheaper if you shop around and find a deal on a motor. You should decide on your goals for the car before you do anything though. If you just want the car back in running condition, a motor swap will probably be your best option.

If you plan to modify the car a good bit, you'll probably want to invest the money and parts to refresh/beef things up while it's apart. Just keep in mind, without being able to tell the current condition of the shortblock that's in the car now, your build may become exponentially more expensive if you find out you need to rebuild part or all of the bottom end. You're looking at 2k + at minimum if that's the case.
 
I notice u said it was fine till it got extremely cold. Was the coolant freeze point good for the temps you had?
 
Here's what I would do; find a long block and do a 1 for 1 swap.

I would do that, but I have looked all over already for 6 bolt long blocks around me. I haven't had any luck really in finding one.

I notice u said it was fine till it got extremely cold. Was the coolant freeze point good for the temps you had?

Yeah it has 50/50 in it with minimum protection of -34F
 
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Innovation Products Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications MyMitsubishiStore.com RixRacing RockAuto RTM Racing STM Tuned

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds

Back
Top