90 Laser, serious starting problems.

[AntiZeroTrip]

Ok this has gone on for too long and I could really use some help. My 1990 FWD turbo laser has been having starting problems. I get in and depress the clutch, turn the key to start and one of 2 things will happen.

1. The car will turn over, and start, and immeadetly die.

OR

2. The car will just chugg over and over like its trying to start but you never get a response from the motor you just hear it turning over.

Now in some cases if I keep the key held to start and give it gas it will start, but the second i let off the key the car dies, wether im giving it gas or not. I have to keep it turned to start for about 20 seconds while i hold the gas. after that it seems like the CEL comes on and the car will run fine.

I thought it was the EGR valve so i took it off and cleaned it out. popped it back on and it didnt change a thing. I thought spark or fuel, but if that was the case I would expect it to continue to cause problems when I drive it. but other than the boost not properly boosting (boost leak or maybe its on a limped fuel map because of the CEL) it will drive fine.

The only things i can think of now is a sensor of some sort. any help?

**UPDATE**

Ok I had the car in the shop and the CEL is from the knock sensor. there is n o apparent engine knock though. My mechanic was tinkering and driving the car and we found out that the MPI (multi port injection relay) which is located next to the ECU is clicking afrter the car turns over and starts, and when the MPI clicks the engines revs will drop and the car will die out. So, we are thinking that the MPI might be bad. OR we have suspicion that the ECU might be the main cause of it all and needs replacing. We hav not pinpointed it just yet. My new questions are,

1. does the MPI relay die off like that without warning?

and

2. Is there anything to give you forewarning that the ECU is going?

Help is appreciated. thanks

 

[Sotarts]

Check fuel filter? Check fuel pressure regulator? How many miles on the car? Vacuum leaks?

 

[RedRain]

Try checking the Maf Sensor(IAT Sensor). Check for Vacuum Leaks like aovsi mentioned. I know in my Eclipse(N/T) it would die out every time you would start the car and it ended up being the Maf Sensor.

http://www.geocities.com/MotorCity/Downs/7678/dsmtests.html

 

[AntiZeroTrip]

hmm, i will have to look into the maf sensor. I wonder when the last time the fuel filter was changed. i havnt had the car for any more than 3 weeks now and so i wouldnt know the last time it was changed. might be a good time to check it out. is it simple to change on our cars? I havnt been able to run a boost leak test just yet. I have a testor built I just need to get a compressor for it. I dont know if its fuel or spark related though, id expect it to happen all the time if it were that.

 

[Sotarts]

Go under hood and follow the fuel rail supply line to the firewall. That thing the hose goes to on the firewall is the fuel filter.

Undo the fasteners from the fuel filter BEFORE unbolting the filter from firewall. Bottom supply line is steel tube, secured just like a brake line at the brake master cylinder.

 

[AntiZeroTrip]

More information about my problem has been discovered and is Updated

**UPDATE**

Ok I had the car in the shop and the CEL is from the knock sensor. there is n o apparent engine knock though. My mechanic was tinkering and driving the car and we found out that the MPI (multi port injection relay) which is located next to the ECU is clicking afrter the car turns over and starts, and when the MPI clicks the engines revs will drop and the car will die out. So, we are thinking that the MPI might be bad. OR we have suspicion that the ECU might be the main cause of it all and needs replacing. We hav not pinpointed it just yet. My new questions are,

1. does the MPI relay die off like that without warning?

and

2. Is there anything to give you forewarning that the ECU is going?

Help is appreciated. thanks

 

[RedRain]

It is a possibility that your ECU is going. If you know of anyone with an ECU try swapping them just to see if it works. You can always take the ECU out and check the caps to see if they are leaking.

 

[AntiZeroTrip]

too bad the 4G63 and the 4G63t ECUs arnt the same, i could swap the one out of my 91 eclipse and try it. how hard is it to open the ECU?

 

[Diplomat]

"too bad the 4G63 and the 4G63t ECUs arnt the same, i could swap the one out of my 91 eclipse and try it." - AntiZeroTrip

Actually, that should work. If we're talking about another 1Ga 4G63 ECU, you may want to try it. If your car starts, turn it off and start it again several times just to be sure, then you'll have your answer.

However, don't go driving around town with your N/T ECU. It will run, but an N/T ECU does not talk to your knock sensor, nor does it operate the boost control solenoid or adjust timing if knock is occuring. Plus fuel and timing tables will be off a bit and you may run lean or rich.

When I test drove my car with the previous owner before I bought it, I noticed the boost guage wasn't working. I asked him about it and he told me that he had to replace the ECU a few months earlier and that the gauge hadn't worked since. So right away I figured he'd picked up a reconditioned ECU and got a N/T one by mistake. I checked part numbers and sure enough, that's what happened.

So your N/T ECU should work. Although the part numbers did change during the 90's, but I don't know if the differences are enough to keep it from running.

"how hard is it to open the ECU?" - AntiZeroTrip

It isn't hard at all. Although it is kind of a pain to get your ECU out of the car. It's in the console below your radio, behind the carpet covered area that divides the driver's and passengers foot wells.

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It's not too tough remove, but you'll beat up your fingers a bit trying to unplug the connectors. Once it's out, remove the four screws on the cover and voila, printed circuit car brains!

Once open, you'll find three electrolytic capacitors in the middle of the board.

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If they're leaking goo, either replace them or buy a reconditioned ECU. Once the capacitors start leaking, they may be shorting. An ECU with leaky capacitors can cause all kinds of freaky problems that'll drive you ape #@%& trying to troubleshoot it.

While we're on the subject, there is something else you should know about your ECU. Many early '90's and even some '91's came with EPROM ECU's. Once you get yours open, you can check to see if you're one of the lucky winners. Check out this page from TMO's website that shows you how to tell the difference between EPROM and Non-EPROM ECU's. So what's so special about the EPROM's? Well those ECU's have the capability of being reprogrammed to some extent. An EPROM ECU can be "socketed" and a modified EPROM chip installed which can be used to make adjustments for certain upgrades such as larger fuel injectors. Just browse TMO's website to see what can be done with an EPROM. Also, if you hope to make some real power down the road, you may find yourself considering an engine management system like the popular DSMlink, which requires the use of an EPROM ECU.

The reason I bring that up is that, if it turns out you have an EPROM ECU, you may want to consider having it rebuilt (if the ECU is truly the problem). As time goes on, there are fewer and fewer 1G EPROM ECU's to go around and they're becoming rather expensive for us gear heads. If the damage is minor, it may be cheaper to have yours reconditioned as compared to buying another EPROM. Of course you could probably get a non-EPROM ECU for $100 or so, if you're in a pinch.

I suspect it may be something beside your ECU causing this problem, but that's just a hunch and I could be wrong. Anyhow, don't worry. If the car runs fine once it turns over, then you probably have an electrical gremlin somewhere and hopefully it won't be too expensive to fix (as opposed to a major mechanical failure).

By the way, if you decide to change your fuel filter, it's a lot easier if you remove your battery first. Good luck.

 

[AntiZeroTrip]

Today I tore out the ECU and opened it up, it looks to be fine with no capacitor leaks.

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I drove it to work today and then when I went to drive it home it decided to act up and be a pain in my butt. I tried to start it for 15 minutes,. and then out of nowhere it just turns over and starts like any new car would. I drove it home and im afraid to take it back out anywhere. so, what should I go about doing next?

 

[ddavisaf]

Take the caps out. Sometimes it can be hard to tell that the caps are leaking until you actually remove them from the circuit board.

Replace them while you have it out. The caps cost like 3 dollars shipped.

Time to go through and test relays and fuses it sounds like.
Next I would make sure my spark plugs are okay. Then check for fuel pressure.

Your battery. Is it tied down with a piece of vinyl over the positive terminal?

 

[AntiZeroTrip]

Ok I replaced the fuel filter, and the car seems to run fine now with the exception of a boost leak.

Thats not to say that my problem might be fixed or not, because having the computer disconnected from the battery causes it to reset, and just because it runs fine now dosn't meen it will later.

The only thing I can think of with the fuel filter is that the car was clogged up and the fuel filter was too, and when I ran sea foam in the gas it cleaned out all the crap and flushed it right into the fuel filter.

anyone have any opinions?

 

[AntiZeroTrip]

Nope nevermind it didn't fix the problem. It seems like whenever i disconnect the battery and the ECU resets, or the ECU is resetted, the car runs fine for about half a day, then its back to the old trouble. what should i do?

 

[ddavisaf]

Refer to my previous post.

 

[half-cocked]

Sometimes when the caps are leaking on the ECU it smells like fish, does yours? Try putting the N/T ECU in, the N/T ECU doesn't have the turbo timing/fuel maps or the provisions for the knock sensor but it will start your car. And yes, the MPI will click if going bad.

 

[AntiZeroTrip]

Hmmm, well i suppose I could plug in the N/A ecu and see if it turns over without giving me crap. that would help me to figure out if it was the ECU or not. The thing is I'm swapping from a 91 2.0 non turbo automatic to a 90 2.0 turbo manual. does that matter with the ECU or MPI? I know the ECU wouldn't control a lot of stuff so i shouldn't drive with my 91 NA ECU in my turbo. The ECU itself looked to be fine, and it didn't smell bad or anything. The MPI will click 5 or 6 times as soon as the car actually starts and will kill the revs with every click. I meen you can watch the revs drop with each click. Would the 91 Eclipse N/A MPI be able to be swapped over to my 90 Laser turbo? If so I may try that too and see what happens.

 

[half-cocked]

Bag the ECU idea, the '90's use a different transistor than the '91-'94's and the ECU's aren't compatable without switching the transistors. But if you have the MPI from the '91 swap it in, there isn't any difference to my knowledge. I would be willing to bet a few bucks that it is your MPI shitting the bed.

 

[AntiZeroTrip]

if you have the MPI from the '91 swap it in, there isn't any difference to my knowledge. I would be willing to bet a few bucks that it is your MPI shitting the bed.

Sweet. I will have to try that and see what happens. I will post a response to that by tomarrow.

 

[AntiZeroTrip]

So I swapped the MPI and its been running fine and turning over and starting right away ever since I did it. I am still skeptical and I think I need to test it more to find out, but so far its been running fine.

 

[half-cocked]

I think you just fixed your car.

 

[AntiZeroTrip]

Well its been a day and a half now, and the car is still starting and running fine. Thanks to everyone who helpped me out. I think its ok now.

 

[half-cocked]

Good to hear, strong work.

 

[Old Mitsu Tech]

Clear the codes and see when the knock sensor code comes back. If you have access to a scan tool drive it and see if it comes on at idle or only under heavy load. I don't have the figures but if it is coming on at idle it can retard the timing which could cause a problem. One thing to remember as I do this for a living. Electronic parts don't always have to have a reason to fail. We had a 90 Talon that sometimes would start and sometimes would crank and crank without starting. Turns out the injector drive circuit which is controlled through the ecu was failing intermittently. It so happened it was an eprom ecu and we had it rebuilt. Problem solved. Sometimes problems fix themselves right in the middle of a diagnosis only to rear their ugly head a few days or even weeks later. And food for thought about new parts. New stands for Never Ever Worked. Take a known good running component from a known good running car. Trust that over a "new" part. Trust me on that one. Old Mitsu Tech

 

[AntiZeroTrip]

Clear the codes and see when the knock sensor code comes back. If you have access to a scan tool drive it and see if it comes on at idle or only under heavy load. I don't have the figures but if it is coming on at idle it can retard the timing which could cause a problem. One thing to remember as I do this for a living. Electronic parts don't always have to have a reason to fail. We had a 90 Talon that sometimes would start and sometimes would crank and crank without starting. Turns out the injector drive circuit which is controlled through the ecu was failing intermittently. It so happened it was an eprom ecu and we had it rebuilt. Problem solved. Sometimes problems fix themselves right in the middle of a diagnosis only to rear their ugly head a few days or even weeks later. And food for thought about new parts. New stands for Never Ever Worked. Take a known good running component from a known good running car. Trust that over a "new" part. Trust me on that one. Old Mitsu Tech

Awsome info. Thank you for your input. I actually did get the MPI from my other DSM that has been running fine. seems like the longer I stick around here the more I learn. and its always nice when techs share their wealth of knowledge. I love this site!