LS1 from 1999 Camaro in a 1990 Miata race car with an issue starting.

• Cranks well
• Has fuel pressure (haven't measured it but I had a fitting that wasn't completely tight and it was spraying)
• Injectors are firing (tested with a noid light and plugs are wet)
• Spark is firing (confirmed holding another plug in one of the wires while cranking and watching/feeling it spark)
• In HPTuners VCM Scanner, I can connect and see cranking RPM

I haven't figured out how to watch the actual cam and crank signals in VCM Scanner yet, trying to do that. I'm pretty sure crank signal is good since I have RPM. From what I understand, the computer is smart and will try firing 180* apart to start it so a good cam sensor isn't necessarily needed, but I'd still like to verify the signal is correct.

I took a log of cranking using HP Tuners VCM Scanner. I'm getting nothing at all for Cam Hi Lo or Cam Lo Hi. I went into scanner chart settings, changed two of the chart variables by selecting Cam Hi Lo / Lo Hi after clicking on PID. Am I doing something wrong? Anything you can tell from the attached log file?

Thanks for any help guys!

 

Are you using a 411 PCM? What is the base tune in the PCM? Do you have a DBW or DBC setup?

Jon
PSI

 

Drive by cable.

PCM from the Camaro wasn't powering up correctly so I bought a 9354896 ECM from SpareECM on eBay.

 

Do you have power at the DLC connector under the dash?

Jon
PSI

 

There is no dash, but yes I have power at the OBD2 connector and can connect using HP Tuners; that's how I got the log I attached to the original post.

 

Any ideas? I'm lost and have tried everything that would make sense to me.

 

Just measured voltage at the coils while cranking and it drops to ~10v. Is this enough or maybe too low?

 

Is everyone as stumped as I am?

 

I will throw something out there and hopefully it can help. I had problems with my 5.3L starting. For over a year. With new plugs it would start decent but once soaked or fouled they would eventually not fire. I did not have the IAT sensor into the intake tract. I had it sitting off to the side. Once i did eventually put in a filter and hose i put the IAT sensor in there and it fires right up now. And runs WAY better. Before, it was a PITA and eventually after trying to start so many times the plugs would foul to the point of no return. I dont drive my car on the road yet but i needed to get it in and out of the garage and therefore i left that sensor lying on the side of the intake.

Its a long shot but throw in some new plugs and mount that IAT sensor like it should be and maybe it will fire. Its worth a shot. If you have spark and fuel it should run or at least buck and spit. I wouldnt be surprised if the plugs are fucked now.

 

Is the VATS set to none or disabled in the PCM tune? Just a thought.

 

Yes, I disabled VATS.

Just futzed with some stuff, unplugged cam sensor and plugged it back in, changed some stuff in VCM Scanner, and now I am seeing the cam sensor and get Cam Hi Lo and Lo Hi both counting up.

Check this latest log.

 

I have a 1999 ls1 from a trans am in a 1991 mustang. I also bought a PCM from spare PCM. Mine has had the VATS deleted also. The first time I attempted to start my engine was while it was on a engine stand. Before I rigged up a make shift fuel system I sprayed a little starting fluid into the throttle body and cranked the engine. It started and ran for a couple of seconds. After I got a fuel system sending 55 psi of fuel to the engine it didn't want to start but finally did. I found that even though my injectors ohmed out evenly I had 3 of them that were plugged with varnish. My point is try to spray a littel starting fluid in it and see if it fires you might have some bad injectors. My engine had been sitting for 7 years. I replaced all of the injectors and it runs fine now. P.S. after I installed my engine into the mustang it would backfire when cranking and then start on the second or third try. A quick check with a scanner showed no cam or crank sensor. I discovered that I had forgot to plug them in. To this day I still don't know how the engine was still able to start and run without these sensors plugged in.

 

Might be the ignition relay; switch it with starter relay which is right next to it in the fusebox closest to the radiator support. I had the same prob and if this is the fix it will cost you a whole 7 dollars.

 

Both relays are exactly the same btw

 

This is a race car and none of that exists.


I finally got it started, twice actually. But it won't start reliably, and when it does it stumbles along while I'm holding the starter until I can hear it actually trying to catch and idle and it fires.
As soon as I gave it any throttle, it died immediately. This is with the MAF unplugged, but I haven't gotten it to fire with the MAF plugged in yet.

 

Did you try new plugs? Was that pcm set up for a MAF?

 

Someone already mentioned this...How long have the injectors been sitting?
They may be flowing, but perhaps they are partially clogged. The plugs can be wet, but not enough fuel for ignition.
Here's one long-shot....the coil plugs might be reversed. On the pass side, the harness could be backward, making a 8-6-4-2, instead of 2-4-6-8. Likewise, the driver's harness can be 7-5-3-1, rather than 1-3-5-7. I don't have the plug color-codes, off hand.

 

PCM has not had anything disabled/changed to run with no MAF.

Injectors were sitting for almost a year. I started the engine in the wrecked Camaro before pulling it so I know it was good then.

 

FWIW. I had plugged injectors but they were completely plugged with new fuel getting through. But ^^^^ this guy may be onto something and i have the color codes handy as i just relocated my coils below my manifolds and copied the colors down.
1 - purple 2 - pink
3 - blue 4 - green
5 - green 6 - blue
7 - pink 8 - purple

Hope that helps. Worth a check.

 

Quote:
Originally Posted by gMAG
Someone already mentioned this...How long have the injectors been sitting?
Quote...gMAG They may be flowing, but perhaps they are partially clogged. The plugs can be wet, but not enough fuel for ignition.
Here's one long-shot....the coil plugs might be reversed. On the pass side, the harness could be backward, making a 8-6-4-2, instead of 2-4-6-8. Likewise, the driver's harness can be 7-5-3-1, rather than 1-3-5-7. I don't have the plug color-codes, off hand.

Quote...SSZ FWIW. I had plugged injectors but they were completely plugged with new fuel getting through. But ^^^^ this guy may be onto something and i have the color codes handy as i just relocated my coils below my manifolds and copied the colors down.
1 - purple 2 - pink
3 - blue 4 - green
5 - green 6 - blue
7 - pink 8 - purple

Hope that helps. Worth a check.


gMAG.....Just a bit more...in speaking with the guy I use to process my injectors, he mentioned that the injectors don't need to be sitting more than a couple of months, before gas starts to congeal.
So, a non-start condition could not only be due to lack of fuel, but to a lack of spray pattern.
In this case, you could try spraying ether in the TB, to see if the engine starts.
Please be careful!