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Discussion Starter · #1 ·
I removed my strong working 1990 c900T motor from a rusted out body and placed it in a N/A 1992 rust free three door that I purchased that had its motor removed. The transfer went well and i drove the car for 6 months locally with no issues. I drove it on a 6 hour trip and the car performed great with no issues during the trip. Once i got to my destination I made a brief stop and when I came out and tried to start the car it would turn over but not start. I had it towed 5 hours back to a Saab repair shop. The car has spark/fuel but will not start. I've owned various Saab's for over 30 years and work on and repair my own cars. I've never not been able to trouble shoot and start a C900 or any SAAB. The car has a new fuel pump, a new/different ecu, the relays above the ecu have been tested.The engine has good compression.The distributor and CPS tested to be working, I had to purchase a 1992 turbo wire harness to fit the 1992 N/A body,the motor is a 1990 B202. Because of the distance that i broke down at, the SAAB shop was closer than my house to have the car repaired. The Saab shop owner has worked on seveal of my cars and has over 25 years working on Saab's. Any idea of what could be the issue.
 

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Vacuum leak? NTC sensor? Idle valve? Low fuel pressure? Bad plugs? Damaged cap or rotor? Without knowing how they are doing their diagnostics, it tough to just jump in and start offering ideas. LH Jetronic is pretty simple. If you are methodical and start at one end and work your way to the other, you will find the issue.
 

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I'm confused about this because you say that the car has both fuel and spark, and that the ecu and cps are good. Are these things all being tested individually and isolated or following the sequence that happens from turning the key to running?
 

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Discussion Starter · #4 ·
I'm confused about this because you say that the car has both fuel and spark, and that the ecu and cps are good. Are these things all being tested individually and isolated or following the sequence that happens from turning the key to running?
The car is at the shop and I am not conducting the test myself the owner is telling me that he has conducted all mentioned testing and still no start. I find that strange because starting a c900 is systematic.
 

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The car is at the shop and I am not conducting the test myself the owner is telling me that he has conducted all mentioned testing and still no start. I find that strange because starting a c900 is systematic.
Well if they are testing each component individually I don't think they're going to find an answer. I'm still confused at the car getting spark...if at the plug, and fuel...if at the injectors, if this is being checked while someone else is turning the key. I honestly don't see how the car would not start if the both are true, or I don't see how the above could be true if the car won't start meaning at some point the car is not getting fuel or not getting spark at the cylinder.

So all that said, maybe you should drag the car home because it sounds like you have more knowledge about the system than the shop? Or maybe they're just running through some quick steps before digging deeper? I dunno...all seems weird
 

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Discussion Starter · #6 ·
Well if they are testing each component individually I don't think they're going to find an answer. I'm still confused at the car getting spark...if at the plug, and fuel...if at the injectors, if this is being checked while someone else is turning the key. I honestly don't see how the car would not start if the both are true, or I don't see how the above could be true if the car won't start meaning at some point the car is not getting fuel or not getting spark at the cylinder.

So all that said, maybe you should drag the car home because it sounds like you have more knowledge about the system than the shop? Or maybe they're just running through some quick steps before digging deeper? I dunno...all seems weird
The shop owner says he has never seen anything like it. He has had the car for three weeks now however he knows that i have 11 other working Saab's so i'm sure he is taking his sweat time in getting me my car back. Scantar, I was thinking the same thing about getting the car towed home and i'm sure i can figure it out. I'm thinking that it has to be something in the rewiring of the car with the 92 turbo wiring harness. It was my first time in turning a non-turbo into a turbo so it was a learning experience not to diffacult. I just wanted to see if anyone had any ideas on possible no start issue. If it had given me any signs while driving I could figure where to start but the car drove flawless for over 5 hours at 75-80 mph.
 

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I'm a little confused about how the '92 harness factors in. All '89 to '93 turbo harnesses are the same.. the only variation is whether it's prewired for EGR or not... I think only the first couple years or maybe just '90 is. But unless you installed EGR and need EGR, there's no difference between a '90 and '92 harness.

Did your install APC? Did you remove EZK?

A car that runs and then doesn't sounds like a Hall sensor or ICM... But you say there is spark and fuel. Will it run on starting fluid? You really gotta go through it methodically... Jumping in right in the middle won't get results. Eventually you can reach something untestable like ECM or AMM or (to some degree) AIC but those are quick swaps to determine if there's a fault.
 

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One thing to check might be the ignition switch to make sure it has +15 power in the start position. Most of the tests are done with the key in run position. If you have +15 in the run position you might pass alot of tests that would fail when in the start position if it is not providing full voltage on the +15 circuit. Just something to throw out there.
 

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Discussion Starter · #9 ·
I had to change the front main fuse box from a n/a to the turbo fuse box. The three connectors for the fuse box are different on a 1990 vs a 1992 I mentioned that because I believe it may be a source of the problem. The car has apc and ezk for a turbo connection every thing was swapped over. The car did have the shifter and ignition switch removed from the donor car and placed in the new car. I will remind the repair shop of that.
 

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Discussion Starter · #10 ·
The shop called me today and said that they checked the compression again and it has zero across all four cylinders now. When the car was checked a month ago it had 150 psi in two cylinders and 90 psi in two others. Not sure how that can happen. Taking the head off for further inspection.
 

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I would be inclined to get that car home as opposed to the shop pulling the head , Something just totally fails to add up with the chain of events described . How can a car loose all comprssion sitting in a workshop where it cant even start ?
 

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At least do a leak down test first... If the issue is the bottom end there is no point pulling the head, the motor has to come out. If the issue is something else like valve sealing or HG failure, then it's the head. 150 is kinda low, but 90 is a motor on the way out. I would try and determine the problem before taking tools to it.

I could see some scenarios where compression does get worse... Like if you have an overfuelling issue continued cranking could cause big wear on cylinder walls. I don't think it's likely, but not impossible.
 

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I've read the post above and here's what I think: When the car first failed to start that was because the valve timing had (spontaneously) shifted. That's sort of a weird thing to have happen but it's one of the few problems that will produce all the described issues. For one thing the cam sprockets are registered to the camshafts with a single tooth in a notch and that tooth can be sheared off under certain (rare) conditions, usually while cranking. That allows the valve timing to shift and results in bent valves. The bent valves can not fully close and therefore you have zero compression. Needless to say you'll also have a no start condition due to the incorrect valve timing and lack of compression. You'll still see a spark on all four plugs (but they will be out of time of course) and you'll still have a fully functioning fuel system but it will not start or even make a single pop. I would lift the valve cover and check the valve timing, easy, cheap and quick.
 

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Agreed valve cover 1st check ....set flyweel at tdc ( by socket on crank pulley ) pop the cover and look at cam timing marks .. If a mechanic hasnt done that small task ( after all the time ) I would be staggered,
 

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Discussion Starter · #15 ·
I stopped by the shop today and the owner had pulled the head and it was fine however he squirted oil in the cylinders and two went to 150 psi and two were 90 psi. So the rings are believed to be the issue. I am going to just replace the motor and I told him to let me have the old motor so that I can pull it apart and just rebuild it. I’ve always wanted to rebuild a c900 motor so this is my opportunity. I have 5 other c900’s so it will be my back up. Thanks for all of the replies. I’ve owned c900’s for 30 years and never saw anything like this. I thought the motor was strong, I would have rebuilt it before sticking it in the new body but lessen learned.
 

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I feel like this shop may not be on top of things. If the wet compression test took things from 0psi to "pre incident psi" then there was zero point in pulling the head... that's a demonstrable bottom end problem. That said, never in my life have I seen a wet compression test restore 150psi.
 

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I would say impossible to take it go from Zero to 150 by doing the test wet . His test results are flawed
Yeah the rings may be worn and comprssion may be down on a couple of cylinders , but that will not stop it starting .
If you have alternate cars and you are obviously not dependant on this one ... Get it out of there and do a rebuild .
I cant help but feel if you let this shop fit another Sewcond hand engine your problems will escalate as will the hole in your wallet . You need to control the destiny .
 

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Discussion Starter · #18 ·
Thanks for the replies, I can understand everyone’s skepticism about the shop owner but this owner is a 30 + year Saab specialist and the only person that I will let work on my cars. we have done business together for many years. Trust is a strong word with me but I do trust him and his opinion. I must have screwed something up in the engine transfer or just over estimated the condition of the engine. I will just let him replace the engine and rebuild the old engine this spring. It will be a fun project I’m sure I will be asking questions when I get into the rebuild. Thanks again for everyone’s replies.
 

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Start stockpiling parts now. There are some real difficulties getting some parts. I had to order valve guides from Lithuania, rings from the UK, timing chain guides from Canada, etc. There are no oversize pistons available, which means either finding used ones or ordering forged from JE (2 month lead time) or Wossner from Europe, etc. It took me nearly six months earlier this year to get everything needed.
 

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If the two low cylinders are next to each other then you have a common head gasket failure instead of the one-in-a-million ring failure.
 
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