2G Cranks and fires but won't start

[raptoranderson]

I'm embarrassed that I even have to post about this kind of thing because I have been working on DSMs for 3 years now, but it's blowing my mind that my '98 GSX won't start and I cannot figure out why

It started and ran totally fine about a month ago. I then did a fusebox relocation for the chassis fuse box in the engine bay and now the car won't start. You can check this link for a video showing what happens when I crank the car:

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It's definitely getting fuel (I can smell it clear as day) and the cylinders all have compression, I'm getting a spark and the timing hasn't been touched since I last worked on the car.

The most recent bout of non-starts I had with my car was from switching over to Speed Density a few weeks ago, but after working on the ECU with EcmLink and doing some basic tuning I had the car idling and running perfectly. I cannot imagine why it won't work now, but I have posted my EcmLink file to this post too just in case I am missing something obvious.

Regarding EcmLink, I used the EcmTuning SD bundle so I am running a GM IAT sensor and an OmniPower 4-bar sensor rewired and installed in place of the factory MAP sensor, both of which are plugged into the old MAF plug through the SD bundle harness. I can only imagine that maybe in the fusebox relocation a fuse blew somewhere or maybe the change in resistance due to lengthening the wires is having an adverse effect on my car

 

[ThunderChild]

Did you make sure to have all your ground connections done right? There's a few systems that tie into ground wires and they can be missed, or not have a great connection occasionally. Did you just lengthen all wires?

 

[raptoranderson]

I did, yes. I lengthened all of the wires and the large white power wires as well as the large black ground wires have all been connected properly as far as I can see. The only system in the chassis fuse box that would appear to make any difference is the motor (20A engine/ moteur) fuse. Would an improper ground for this fuse cause the engine not to start? surely it wouldn't crank at all if it wasn't working, though I'm not 100% sure what this fuse is for specifically ...

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[ThunderChild]

Check all the fuses for continuity, and I'd look at the power transistor or coil ground after that. I don't have access to alldata from home, but I suspect you have an ignition issue, tho it almost seems like a mechanical timing issue from the video.

 

[raptoranderson]

I thought timing too, but none of the timing systems run through the engine bay chassis fuse box I guess I'll start by stripping the chassis loom out of the engine bay and checking over my work with the fuse box. Any tips or tutorials regarding removing the chassis loom? I don't personally think it'll be difficult, but I have thought that several times when working on my DSM and every time I have underestimated the situation

 

[motomattx]

Try replacing the coolant temp sensor (two wire one), or maybe just log it if you can.

 

[raptoranderson]

Can that system be tested or logged without the engine running and with just a key in the ignition and accessory power on? It's a good point though because I've read that the engine sometimes won't run because it will lean/ richen the fuel mixture based on what it thinks the coolant temp is ...

 

[pauleyman]

You have a 30amp ign fuse also.

 

[doubleclutch]

Seems like it is briefly firing, just wont stay running. I would hope this means you are getting fuel, spark, and compression. Is it getting flooded with fuel after it gets out of the cranking mode?

Also, i think you should have the "disable maf compensation w/SD operation" checked.

 

[raptoranderson]

The 30A ignition switch fuse and 20A motor fuse are both working. If you pull the IS fuse the car doesn't have any accessory power, after I put it back in the car gets accessory power, and if you pull the motor fuse the CEL doesn't power on for 5 seconds, after I put it back in it does.

I checked the connections on the coolant temp sensor and I don't see any breaks in the wire or bad connections. Wouldn't the car start if the sensor failed because it assumes the car is warmed up as a fail safe?

EDIT: I locked the temp sensor reading using ECMLink and the car wouldn't even come close to starting, it just cranked and didn't try to sputter to life at all

 

[jakk220]

I can't view the log right this minute. How does the MAP sensor reading look when this is happening? When my car did the the last time I had a bad OMNI 4 bar map sensor that was brand new. I actually had 2 go bad on me before I contacted Omni directly. The said they made some recent changes and warrantied out my old one. Just something to check.

 

[raptoranderson]

I have used this MAP sensor before countless times and it has had 0 issues. It's possible that the sensor crapped out on me without my knowledge I don't see any way of logging any MAP values, but the average MAF value was 13.9 Hz, and I have the MDP locked since i am running speed density. During cranking, when the RPMs would bog down as the engine began to fire and try to run the MAF would jump from between 2 and 4 Hz up to between 27 and 38Hz before the car died again and the starter motor started cranking it a second time. When logging Baro, the value stayed at 30.1 inHg at all times throughout the entire cycle of cranking and not cranking the car

 

[jakk220]

I have used this MAP sensor before countless times and it has had 0 issues. It's possible that the sensor crapped out on me without my knowledge I don't see any way of logging any MAP values, but the average MAF value was 13.9 Hz, and I have the MDP locked since i am running speed density. During cranking, when the RPMs would bog down as the engine began to fire and try to run the MAF would jump from between 2 and 4 Hz up to between 27 and 38Hz before the car died again and the starter motor started cranking it a second time. When logging Baro, the value stayed at 30.1 inHg at all times throughout the entire cycle of cranking and not cranking the car

Ok so your MAP sensor is being logged as "boost". The MAF reading does not matter as you are using speed density. Post a log of you cranking the car. When my MAP sensor died, the reading would either drop to -28.9 and the car would stall, or it would be stuck at -28.9 all the time. A log will definitely help.

In the meantime you could try to switch the car off of SD, and hook up a MAF sensor. Or you could try another MAP sensor. From the video it looks almost identical to what my car was doing. It is worth a shot.

Also idk what injectors you are using, but it looks like the car is scaled to stock injectors. So if you are not on stock injectors, that needs to be adjusted.

 

[chrysler kid]

Do a boost leak test dammit.

You can't just plug in a computer to fix your problems. You probably popped a coupler or have a large boost leak

 

[raptoranderson]

Regarding the coolant temp sensor theory,

Ok so your MAP sensor is being logged as "boost". The MAF reading does not matter as you are using speed density. Post a log of you cranking the car. When my MAP sensor died, the reading would either drop to -28.9 and the car would stall, or it would be stuck at -28.9 all the time. A log will definitely help.

In the meantime you could try to switch the car off of SD, and hook up a MAF sensor. Or you could try another MAP sensor. From the video it looks almost identical to what my car was doing. It is worth a shot.

Also idk what injectors you are using, but it looks like the car is scaled to stock injectors. So if you are not on stock injectors, that needs to be adjusted.

I am using stock injectors so those are all correct, and the Boost reading is staying at -28.9 the whole time during cranking. However when the car was running and driving about a month ago the Boost reading stayed at -28.9 too during startup and idle, so I don't think this is the issue.

As for boost leaks everything is hooked up as it should be. I'm still using the stock side mount intercooler for the time being so the plumbing is relatively straight forward, but I have started a car with a serious boost leak before and it starts and runs for a second and then dies out again. This is not that

 

[doubleclutch]

Never hurts to do a boost leak test. I was on stock piping on my Gs-t and found that it had torn at the TB elbow causing a huge leak. You never know till you check.

Your boost reading shouldn't stay at -28.9, that would be an impressive amount of vacuum. What does your boost gauge show during cranking? They should match. I agree with Jakk, you can try plugging the MAF back in or trying another MAP sensor.

 

[jakk220]

Regarding the coolant temp sensor theory,



I am using stock injectors so those are all correct, and the Boost reading is staying at -28.9 the whole time during cranking. However when the car was running and driving about a month ago the Boost reading stayed at -28.9 too during startup and idle, so I don't think this is the issue.

As for boost leaks everything is hooked up as it should be. I'm still using the stock side mount intercooler for the time being so the plumbing is relatively straight forward, but I have started a car with a serious boost leak before and it starts and runs for a second and then dies out again. This is not that

Just as double clutch said, your boost reading should not be stuck at -28.9. You either have a wiring issue or your MAP sensor is dead.