Depressed Express Van Too Many Hands in the Cookie Jar

Michael Mobile Technician Utah Posted   Latest  
Case Study
Electrical
Programming
1998 Chevrolet Express 2500 5.7L (R L31) 4-spd (4L60-E)
Crank / No Start

I get called to a shop that has been fighting an Express Van for two weeks. Their customer took to a transmission shop and after the transmission replacement, the van would not start. The van was towed and sat dead. The report was good fuel pressure at 55lbs and good spark. I get there and do some initial testing. I am getting spark in the distributor cap but not out of the distributor cap. So I take the cap off and the contacts are very worn. We replace the cap and rotor. A little stumble then nothing. Just crank no start. I notice that there is corrosion on the PCM surface. I do a quick scope of the injectors and the pattern does not look right. Power side was checked to fuses. I tell the shop that likely the contacts between connectors and PCM are corroded. Take the PCM out and check it.

I get a call the next day. We have the new computer. So I go over, program computer and get the same result. I ask the shop owner if the van has the updated fuel injector assembly. Surely in 20 years it was replaced? He said that they put in a rebuilt engine and that was replaced at the same time. OK, well I am scratching my head at this point. I told the customer I would work on a solution over the weekend. I consulted with a guy that knows his GM stuff. (He knows who his is here). He tells me less that 62lbs pressure will fail to fire poppet type injectors. Something I had forgotten after nearly two decades. I get a call from customer. He tells me that he has replaced the injector assembly. (So it was not replaced last year as thought) Now it starts and stalls. I run over and start doing some testing. Meanwhile I am handed a bundle of wires that were removed / exchanged from the Van.

WTH! At this point I am real frustrated. I grab my TunerCat programmer, read the PCM file, check the no VATS box and program back the file. Wait 30 seconds and it starts! (So let me backfill some information here.) The immo data was looked at quite thoroughly during the initial testing and after the PCM was replaced. Everything was in order. No immo lamp and according to scan data, no VTD shutdowns for anything. Not sure why the immo was so mad or why it did not report an issue. (No codes, no foul data.) I am so glad that I had an avenue to go to.

I don't think the cap and rotor were an issue. It was most likely my barnyard test. The fuel injection spider assembly was definitely the main culprit. (I really think the fuel pump is also compromised since the fuel pressure did not change after spider assembly replacement) The immo issue was most likely introduced between the transmission shop and the repair shop changing parts and removing wiring. By removing VATS all together the introduced problem is solved.

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Helpful
Missing Tests
Sam Mobile Technician
Michigan
Sam
 

Which tuner CAT programmer are you using?

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Michael Mobile Technician
Utah
Michael
 

TunerCat OBDII Roadrunner, I purchased mine from Moates​.​net The roadrunner is not required when programming. I used TunerCat OBDII for this job. I also have the original version that programs chips for the legacy ECUs.

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Scott Owner/Technician
Michigan
Scott
   

I have tunercat obd2 as well as pretty much every definition file available :) Honestly the vehicle was probably in vats fail enable mode when the transmission went out and then for the first guy to clear codes/ disconnect the battery it was his unlucky day

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Michael Mobile Technician
Utah
Michael
 

I see that someone mentioned "missing tests". Unfortunately, as a mobile technician it is not easy to take pictures and do great documentation. Most of the time we are working against the clock and have other jobs stacked up waiting. It is common to be working outside which does not encourage one to spend time with documentation. If one has a specific question about the tests run, I would be…

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Agree
Funny
Interesting
Nolan Technician
Bahamas
Nolan
 

Thanks for this diagnostic story , i try to read all of your posts every one of them to me are like an adventure please keep these great post coming i truly appreciate you taking your time to and all the best !!!!

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Michael Mobile Technician
Utah
Michael
 

Thank you Nolan, I try to make my diag stories fun to read. It is much better to laugh than cry. Best regards, Mike

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Ð Awarded
Agree