Car shut off when coming to a stop on the freeway. I dont have spark and i am bringing home a noid light tommorow to check for injector pulse. My question is when i hooked up my scanner and was cranking the car over i wasnt getting an rpm reading on the scanner. I thought that would point me in the direction of a crank sensor problem. But one of the guys at work told me that these vehicles get there rpm reading off the cam sensor. Which one gives the ecm the rpm reading?
No start
- Thread starter jay dcpt
- Start date
turbofish38
Le Pétomane
- Joined
- Dec 3, 2002
Pull the cam sensor cap off and see if the reluctor wheel has broken off or check to make sure that the cam sensor is turning when you crank the motor over. If it aint turning than you got a busted timing chain. I've had a few(2) chains break in my time. One went out with a bang and the other with out any dramatics.
Will do thanks for the quick reply.
- Joined
- Feb 18, 2006
Check fuses first.
If still no spark check crank sensor. Make sure harmonic balancer is tight. I've seen it come loose and walk out of the sensor.
If still no spark check crank sensor. Make sure harmonic balancer is tight. I've seen it come loose and walk out of the sensor.
84BuickGNYorkPA
Daily Driving Buick V-6 Turbo's 1979 - Present
- Joined
- Jul 5, 2005
The Ecm gets it's RPM signal from the Crank High line. The signal is generated by the Ignition module and there won't be any output until you get at least one cam sensor pulse. Now having said that I never see an RPM signal on powerlogger until the engine is running. The Factory tach should give a signal though
Ok this is where im at. The car has injector pulse, all fuses are good and today i had spark and it would sometimes backfire out of the throttle body like the timing was off. So i took out the cam sensor and everything looks good there. I the checked compression on #1 and #2 and they were right around 140. So im thinking that tomorrow (in between cars that i get paid to fix) I am going to pull out the intercooler and fan so I can get a good look at the balancer and crank sensor. Im thinking my problem is somewhere in that area. Does it sound like im on the right track? Has anyone ever seen one of these motors jump time enough to where the car wont start but the chain doesnt break? I would think that would probly not hapen. The car is pretty much stock with 120,000 on it. Any advice? Should i be looking in a different area? Also just to make sure, is the only fuse box on these cars the one by the pedals? Thanks again every one.
- Joined
- Feb 18, 2006
If it has spark and was trying to kick, check the ring on the cam sensor. Sounds like you broke the tab.
novaderrik
Well-Known Member
- Joined
- May 12, 2004
is there gas in the tank, and do you have fuel pressure at the rail?
when my stock fuel pump died, it would try to fire and would backfire once in a while.
when my stock fuel pump died, it would try to fire and would backfire once in a while.
Yes there is gas in the tank. And yes there is fuel pressure at the rail. I pulled off the cam sensor and the cap looks fine, and i pulled the shaft out and everything looks ok. Now when you talk about the ring on the cam sensor are you talking about the part that is held on by a screw at the top of the shaft with a window in it for the magnet? because that is fine. It is not loose and turns with the engine when you crank it and by hand after i removed the shaft itself.
- Joined
- Feb 18, 2006
Yes, there is a tab on that wheel that commonly breaks off. The wheel will move slightly and throw off injector timing. The motor will do as you described when you try and start.
Sounds like the cam sensor needs to be set, it may have been right on the edge and moved slightly (enough to make it quit). Or the plugs are so fouled it won't run...
Well the plugs are not fouled. And im not sure of the tab on the cam sensor that your talking about. I guess i would have to see a picture of a new one. but it doesnt look like anything broke on it. (that i can tell) I removed the intercooler and balancer tonight to get a good look at the crank sensor and nothing is damaged and the balancer bolt was not loose. Judgeing by my compression readings I find it hard to believe that there is a timing chain failure. Maybe im missing something when im looking at the cam sensor and shaft. I dont see a tab that you guys are talking about. When i started working as a tech it was only the series 2 3800 so im learnig as i go with these old 3.8s. I would hate to take off the timing cover and find that all is well. I think i need to find a pick of a new cam sensor. There has to be something that im not seeing. Once again I really do appreciate all the help. Im looking in this area because when you would crank this thing over it just sounds like the timing was off. and it had all the symptoms of that. I need to do a search on cam sensors maybe i can find a pic of a new one. thanks again ill post back where im at.
0
0
Ok so when im looking at the top of the cam sensor shaft there is the ring held in by a screw and the ring has a window in it for the magnet. Now towards the middle of the ring where the screw is there is a very small rectangle and im guessing a small tab should be right there. Is this correct?
hope this helps..
Cam Sensor
Cam Sensor
Thanks one fast 6 that helped alot. I took the screw out of the top of the shaft and pulled off the ring and it was clear to me then what the tab that breaks is. and mine isnt broken so im not thinking cam sensor. So over the weekend I am going to take it apart to the timing chain just to have a look see. And like you said replace the chain anyway because of the mileage. Does anyone have a link on replacing the timing chain? If not i supose I could probly find an old shop manual at work somewhere. I can not remember the last time i was scratchin my head this much on a simple no start. Damnit!
DaySleeper
Member
- Joined
- Jul 27, 2010
One time at band camp... No really... my car shut off and I had spark but my injectors were NOT pulsing. I wiggled the harness to injectors and sure enough, it fired up and then I killed it again by wiggling the harness. The way I fixed it since I was broke was running an extra ground wire to the injector harness and I drove it like that for another 50K miles.
84BuickGNYorkPA
Daily Driving Buick V-6 Turbo's 1979 - Present
- Joined
- Jul 5, 2005
There is not much to replacing the timing chain, get #1 cylinder up to top dead center, both valves closed, before clocking new timing chain/gears, by lining up the dot's. on the gears. If you go with the double roller chain don't put the chain tensioner on the car like I have in the picture, it will chew it up.
Chuck
Chuck
