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Dan
Dan, ASE Certified Technician
Category: Pontiac
Satisfied Customers: 2270
Experience:  20 + years working on cars 9 years GM Tech
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97 Pontiac: it cranks..MAP sensor..camshaft sensor..fuel injectors

Customer Question

My 97 Pontiac transport has good fuel pressure, good spark, it cranks over but will not start. Possible MAP sensor or camshaft sensor problem? I don't think the fuel injectors are pulsing. Checked ohms in all 6 injector coils, ohms were within specs. Replaced fuel pump and filter because van has so many miles on it even though pressure test o.k. [Rebuilt engine about 15000 miles ago] Engine began stalling but would restart after sitting a while. Had good spark all along. Any help would be appreciated.
Submitted: 4 years ago.
Category: Pontiac
Expert:  Dan replied 4 years ago.
Hello Customer,

If you got spark and fuel pressure, Next thing to check to see if the injectors are pulsing. You can't get to the injectors to install a noid light to see if it is pulsing unless you remove the upper intake. You can check it at the big connector in the back. an easier way to start is to spray a little carburetor cleaner or some starting fluid in the intake and see if it will run on that. If so, We need to check for injector pulse.
Customer: replied 4 years ago.
I'll have him try to run it on starting fluid, then check for power at the large injector harness near the alternator and use a low voltage circuit tester to check for pulse. If it won't fire on starting fluid, of course we have a different issue here. If we don't have injector pulse, what would be the most likely cause?
Expert:  Dan replied 4 years ago.
One thing is to make sure he security light goes off after you crank it. The theft system can prevent injectors from working. The engine module controls the ground for the injectors. Would need a scan tool to test inputs and outputs to module. Does all accessories work in the van.
Customer: replied 4 years ago.
One more thing......let's say the security light does go out after cranking but there's still no injector pulse? What would you look for next? Also is it possible it's a bad key? That resistor in the key could be bad, I've heard of that happening. I could have them try to use the spare ignition key........
Expert:  Dan replied 4 years ago.
most of the time it won't crank with a bad key and the security light would be on. But the body control module may no send the signal to the engine computer to allow to stay running. Yo would need a scan tool to see if that is happening.
Customer: replied 4 years ago.
From what the schematic on Alldatadiy.com shows, the body control module can prevent the fuel pump RELAY from sending power to the fuel pump. Are you sure the body control module can prevent the injectors from pulsing? If so I'll have it scanned like you're telling me.
Expert:  Dan replied 4 years ago.
The Content Theft Deterrent (CTD) system disables the fuel delivery to the engine when the Body Control Module (BCM) sends a "go" or "no go signal to the Powertrain Control Module (PCM) . The PCM then enables or disables the fuel injectors.
Customer: replied 4 years ago.
O.K. a few more things and I'll leave you alone......if it IS the CTD system, can you reset it with a scan tool? What would cause the system to act up? I'll see if I can find the location of it on Alldata. {If I knew what kind of signal it sends to the PCM, I'd love to duplicate it if it's what's going on} Again, if it's not the CTD system, what are a couple other possible causes? Again, no DTC's were set, no MIL illuminated.
Expert:  Dan replied 4 years ago.
Do all the accessories work inside the van. Power locks and windows?
Customer: replied 4 years ago.
I'll have to find out from my wife or her dad. She's visiting in Arizona right now. What if all the accessories do work? How would this be related?
Expert:  Dan replied 4 years ago.
these are controlled by the body control module which if it was not working, It may not send the signal to the engine computer to allow the injectors to pulse. These modules get water on them from the windshield leaking on them.
Customer: replied 4 years ago.
Maybe it would be worth a try to get a junkyard BCM and swap it out. I found out the location of it. Now, if it's NOT the BCM, what else have you seen that has caused a no injector pulse condition if it's not the PCM, power or ground issue? A bad cam sensor or MAP sensor?
Expert:  Dan replied 4 years ago.
Cam or crank sensor can cause it. there are 2 crank sensors one behind the crank pulley and one on back
See the wire melted that goes to the coil from the rear crank sensor. They get too close to the exhaust crossover pipe and burn a hole in them.
Customer: replied 4 years ago.
Do you know the reason why no DTC is set a lot times when there's a problem? Sure would be nice if a code was set.
Expert:  Dan replied 4 years ago.
did you check it for a code or just going by the service engine soon light?
Customer: replied 4 years ago.

A friend down there has a scanner and he supposedly scanned it, but what I'm afraid of is if it's a cheap scanner, it may not pick up a manufacterer specific code, just a generic code. I was told that the service engine soon light is NOT illuminated. This can make for a real sweet time figuring this out. I know what you mean about a scanner, I have a 4000 dollar one here in Wisconsin, I bought it used for 500 bucks. My best bet may be to just have it towed to a GM garage but if it takes them all day to fix it, it'll be more than the van is worth. It has 280,000 miles on it but it's been maintained well. I know you can test a lot of sensors by backprobing with a DVOM, but that would drive my father in law batty down there. [I've been a mechanic pretty much all my life, I'm 44 years old but don't work on GM light duty all the time like you]

Expert:  Dan replied 4 years ago.
Some scaners wont pick it up unless it fails it on a drive. If it wont start, it cant run the test.
If you take it to a shop and gets someone who knows what they are doing, They can have it diagnosed or have a finger pointed in an hour.
Customer: replied 4 years ago.
I agree if you get a good technician it'll be fixed quick, but if not.........Dan, there are three types of BCM's, type 2, 3, and 4. I'm trying to figure out if ONLY type 4 has the fuel injector disable/able function or do they all have it? I found out how to get a flash code for the type I have in our van. Pull the BCM PRGRM fuse, etc.
Expert:  Dan replied 4 years ago.
they used to go by the color on the label on the bcm
Customer: replied 4 years ago.
O.K., I'm pretty sure that only type 4 would have the fuel disable, because the "content theft deterrent system" comes with only the BCM type 4, but I'll make double sure. {The fuel disable is part of the CTDS} To be sure I could have my wife pull that fuse and get the flash code. Well Dan, thanks a lot for your help. I won't press the Accept Answer button just yet, I'll give you time to add any other comments here, I appreciate your help.
Expert:  Dan replied 4 years ago.
Thats fine, I haven't gave a good answer to fix your issue yet.
Customer: replied 4 years ago.
Hey Dan, good news. I talked to my wife and she said it started today, she took it for a short test drive and the MIL came on, then the engine quit running. It started after a while and they limped it home. I told her to do what she has to do to get the code out of there. This should definately help narrow this down. Sucks that I put a new fuel pump in it, but I didn't trust it anymore anyway because of high miles on the van, who knows when the fuel pump was gonna quit. Should come up as a sensor code I hope.......I can't wait to find out. I'll keep you posted.
Expert:  Dan replied 4 years ago.
Let me know

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