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1990 Mirage Fails to Start
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Paul Koala
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Nov 28, 2012, 6:26 PM
Post #1 of 18
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1990 Mirage Fails to Start
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I'm working on a 1990 Mitsubishi Mirage (1.5L 4-cylinder) that has been sitting for many months. I just replaced the cylinder head (it had blown a gasket due to overheating and was in pretty bad shape). Afterwards I soon found out the fuel pump had failed so I replaced it as well. Now the engine fires just a little when I first turn it over (after it's been sitting awhile) and then just cranks without firing at all.
The diagnostics I've already done:
- I have checked the ignition timing with a timing light on the camshaft timing mark.
- I have double-checked the firing order.
- I have checked that all the spark plugs do spark (outside the cylinders).
- I have removed the fuel rail and confirmed that the injectors are spraying (I know that's a bad way to test the fuel pressure, but since the car doesn't have a port I couldn't conveniently attach a gauge).
- I have checked the compression on the cylinders and they all reach at least 85 psi.
I know y'all may really hate these threads about old cars that have been sitting and won't start, but I'm hoping to get some hunches I can explore.
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Paul Koala
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Nov 28, 2012, 6:44 PM
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Re: 1990 Mirage Fails to Start
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It's true that two of the cylinders are around 85 psi which is concerning. The other two are around 110 psi (good?). You think that's a possible cause for a total failure to start? Regardless, how do you think I should go about diagnosing/correcting the compression problem?
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Discretesignals
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Nov 28, 2012, 6:49 PM
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Re: 1990 Mirage Fails to Start
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Disable the injectors and spark by unplugging distributor electrical connector. Remove the spark plugs and put a couple T spoons of oil down into the cylinders. Crank the engine couple of times. Recheck your compression. When you check compression be sure you have throttle wide open.
Being overheating there is the possibility of ring damage. Rings can also be sticking from sitting so long.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Nov 28, 2012, 6:50 PM)
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Paul Koala
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Dec 1, 2012, 8:58 AM
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Re: 1990 Mirage Fails to Start
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First, thanks for pointing me in the right direction. It certainly seems that inadequate compression is the problem. However, I'm still not sure what to make of the engine's behavior.
When I oiled the cylinders as you said the compression pressures went up to around 150 psi on all the cylinders. The engine started but only ran for a few seconds before dying. When I rechecked the compression pressures they were all back down to around 100 psi or lower.
Of course I considered that there might be a serious problem with the head installation but the odd part is that oiling them and turning them over got the compression back up again only to let it fall again as soon as the engine was started the second time!
BTW, to address the overheating: the head gasket was actually replaced after the first blow and the engine ran fine for several months. However, the second gasket blew after that (not because of overheating) which is why I decided to replace the whole head.
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Discretesignals
Ultimate Carjunky
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Dec 1, 2012, 9:13 AM
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Seems the rings have a problem sealing. Adding oil helps the rings seal and the compression comes up. When the oil goes away (burned off) as the engine is running, the compression goes away.
Either your pressure is leaking past the rings or for some mysterious reason the cylinders are being washed out. I really don't think it is a wash out problem, because washing doesn't usually happen as the engine is running. Washing usually happens during cranking.
What you could try is running the engine on propane or brake cleaner (flammable kind) with the injectors unplugged. If the engine runs on propane or brake cleaner and the compression stays normal, you have a wash out problem.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Paul Koala
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Dec 1, 2012, 12:44 PM
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Hmm, I'm going to suggest a theory and maybe you can tell me if it's remotely plausible.
When I first put the distributor back in I was not careful to get it indexed correctly. I made sure the spark timing was right but I didn't realize that the fuel injection might still be timed incorrectly. I fiddled around with it for awhile before correcting that problem.
Is it possible that the cylinders/rings were severely damaged simply from cranking the engine with them totally washed out? Apart from that I can't figure out what could have changed since the car was running (albeit with a blown head gasket) when it was parked.
Obviously I don't want to take the head back off unless I'm sure it's necessary so perhaps I'll try the propane idea if I can't come up with another plausible explanation...
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Hammer Time
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Dec 1, 2012, 1:24 PM
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If that blown head gasket caused a severe overheating, the rings and cylinder walls will get damaged.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
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Dec 2, 2012, 5:36 AM
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Just some comments/thoughts: How long did this sit in what conditions? The wet (with oil) compression test about proves that lack of enough compression is the problem but hasn't targeted exactly what quite yet.
Sitting there pistons + rings just stayed where they were and whatever exposure to the elements had some time. Cylinder wall galling shown in an extreme like this........
would be fatal for that engine. That you probably could see with a lab type scope thru spark plug hole. Another is general gun rust with the piston rings not really doing their thing flip flopping microscopically which make a lot of difference in their effectiveness.
That could correct with forcing this to run as mentioned. The galling if present wont self correct so at best would be an oil burner ending in game over.
My point is the wild swing in compression tests should be the #1 concern IMO as going from less than 100 to 150 is quite a jump and was uniform to all if I read that correctly,
T
(This post was edited by Tom Greenleaf on Dec 2, 2012, 5:40 AM)
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Smogguy83
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Dec 4, 2012, 2:58 PM
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Re: 1990 Mirage Fails to Start
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Your valve timing jumped a tooth for sure.
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Hammer Time
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Dec 4, 2012, 3:12 PM
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Smogguy83.......... stop posting nonsense. You have no idea what you are talking about.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Paul Koala
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Dec 5, 2012, 11:48 AM
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Thanks for the thoughts, guys. I don't think there's really severe damage to the cylinders because they looked okay when I had the head off (recently) and the engine turned over smoothly by hand. It sounds like the rings may have some significant deposits on them, though, or perhaps even corrosion damage.
I'm thinking about adding some B12 mixed with oil to the cylinders and cranking the engine to help clean them out. Do you think that's worth trying? I really think I'm going to have to take the head back off but I want to try what I can first. 
Thanks again for the help, guys. This has been a bit of a slow project but I'll be sure to follow up once it is resolved. 
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Hammer Time
Ultimate Carjunky
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Dec 5, 2012, 1:14 PM
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There's no such thing as "Mechanic in a Can". The only person that benefits from those additives is the guy that sold them.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Paul Koala
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Dec 5, 2012, 6:02 PM
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Well I took the head back off this afternoon and popped a piston out. Apart from the lower bearing being a bit rough everything seems okay! 
The only thing that looks funny is that the gaps in the relaxed piston rings are a bit different from each other. Is it possible the rings are not exerting enough pressure on the cylinder walls due to the overheating (even though they look fine)? I must admit I have no idea how stiff they should feel...
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Paul Koala
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Dec 6, 2012, 8:22 AM
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Okay, so this is what the rings look like:
Any thoughts?
EDIT: I also checked the cylinder walls and apart from a single scratch on the third cylinder they look fine and are smooth to the touch.
(This post was edited by Paul Koala on Dec 6, 2012, 8:25 AM)
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Hammer Time
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Dec 6, 2012, 8:48 AM
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Visually looking at a piston ring isn't going to tell you anything.
I hope you didn't remove it that way with all the ends lined up on one side.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Hammer Time
Ultimate Carjunky
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Dec 6, 2012, 10:28 AM
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The testing needs to be done in the vehicle while it's still assembled. The wet/dry compression test said a lot but I think I would have done further testing before tearing it down. You don't have any options now.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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