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Howdy gang,
A friend of mine has a 1997 GMC 4x4 pu with 5.7 auto.
Spins like crazy but no spark. It sounds like it is spinning with out the compression stroke.
Is there any way to test to see if the crank sensor is bad-- or what should we check to get him going again
thanks
hank
I'd put a code reader on it and see what it spits out.
Ken's right, read the codes first and see if the car will tell you what's wrong. The crank position sensor is one of those that's hard for the normal backyard mechanic to check. You have to check the waveform with a scanner or oscilloscope and make sure amplitude and frequency remain consistent during crank, and you can check the resistance against specs with an ohm meter. Most guys I know try to eliminate other possibilities, then invest in a CPS and see if that fixes it.
does it have a low pressure sending unit that has gone bad that's not allowing it to fire
Gee!! Can you guys imagin where we'd be if we were working on a car from the 60s..A lot cheaper and easier to repair...Are we going backwards ???
Alot of the stuff is just the basics like back in the day Charlie.Gas and ignition.So if he has no spark,a ignition modual/coil(sp?) can go bad just like the coils of days of old.
I once got my wifes car started and running by spraying her mothers hair spray into the intake----fuel pump was going bad and not enough initial pressure for the injectors---ran weakly, but I drove it like "milking a mouse" for the 850 miles home!!!!!!!!!!!!!!!
I finally got back to my pals GMC and plug in my code reader and it came up with zero fault codes.
The check engine light was not on.
He just drove it where it is parked and it would not start the next day
spins but no spark
anybody have a idea what to check next
thanks
hank
Did you check for no spark ??? May be fuel pump??
I pulled #1 spark plug wire and stuck a old plug on and had it sitting on the exhaust manifold cranked the engine over- no spark
owner said he smelled gas I didn't smell any
No spark at plug check coil wire. They did have problems burning coil wire.
U should really disable the fuel system by removing the fuse or relay, other wise ur dumping raw fuel into the cylinder that won't be burned. If the fuel starts to evaporate out of the cylinder and ur spark plug fires, you can start a fire and possibly lose your eyebrows...I've seen it happen- Safety first:toocool: fuel, spark and compression are the things to check when the car won't start. if theres no spark, i agree with sg4356. try swapping some of them around and see if you get any spark with a different wire. its odd that no codes are being thrown, which leads me to believe the computer may be bad... if none of the coils spark when u switch them up, most likely the computer is at fault:eek: good luck
Yeah, I know, kind of far off thread but a few weeks back I got a phone call from a young guy who had bought a little '61 Olds F-85 (aluminum) engine. He said he had some questions and one of my nephews told him "Call my Uncle Jim. He'll know." He asked what is dwell angle and what is it supposed to be for that engine.Quote:
Originally Posted by cffisher
Heck! I don't know that and I never did. I have never owned one of those little cuties. What nephew was really telling him was that Uncle Jim is one of those eccentric old toots who never throws anything away, and somewhere in that big pile of crap he lives in is the information he needs.
I found the information.
Then the kid called me back about a week later and asked if I had torque figures for that engine.
I did.
Senility can be kind of fun sometimes.
Jim
sorry about not getting back about this but our email server has been down--
it turned out to be faulty fuel pump-- we ended up replacing the pump and fuel gauge sender
cheers
hank
Hey Hank,Quote:
Originally Posted by TOW'D
Thanks for taking time to close the loop!!
You most likely wouldn't smell fuel when it's a bad pump right? Maybe he didn't really smell gas or am I wrong? (just trying to improve my own diagnostic skills..)Quote:
Originally Posted by TOW'D
I had a similar issue with a 5.7 chevy truck not starting, after running rough for a few days, stalling etc..
Turned out to be a corroded distributor. It was so bad chunks of the reluctor, (I think it was), were falling out when I pulled the cap off. I gather GM don't vent the cap area, and condensation over the years, finally takes it's toll.
A Vortec truck engine runs the fuel pump for three seconds when the key is turned on. You can listen for the pump and the pump shutoff. When the engine is cranking, there is no fuel until there is oil pressure (that's why there is a separate circuit in the oil pressure sender on this engine).