Help! it cranks but won't start.
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Help! it cranks but won't start. Well, I did a little bit of search on it but nothing really helps. I finally finished installing the engine back into the car, and finished my new wiring harness for the dual external fuel pumps, I tried to fire her up but it would just crank and crank but won't start. I already doubled checked all the wiring harness, fuses, sensors and no luck. I then pulled the #1 plug wire to see if there's any spark while cranking...nothing, no spark at all. I then pulled a couple of the new spark plugs to see if there's any sign that the injectors were spraying...but plugs are bone dry. Needless to say, I'm really frustrated and bumed-out. I'm just about ready to give-up on this and throw this stupid car away...
. I'd really appreciate any help as to what could cause this. Thanks!
. I'd really appreciate any help as to what could cause this. Thanks! Thread Starter
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cablebandit, I just did that and tach DOES NOT move while cranking, are those sensors known to go bad all of the sudden? At first, I thought I got the map sensor wire connected onto the cam sensor and vise versa, but I don't see how you can get those connectors plugged into the wrong ones. Do you happen to know if the cam sensor has 2 or 3 wires???
Well the cam sensor and the map sensor look almost identical and can be plugged in wrong although I haven't found the cam sensor to keep a car from starting, it just makes it crank a while longer. FP? Have you made sure you have it and the grounds on the back of the head have to be good for the coils and the injectors to work. And well the lack of info leads me to ask for more if you would like further help. You didn't state weather it was just a motor replacement or did you put an LS2 etc... Did you rebuild your original motor use the same crank or what? If not make sure it is a 24 tooth reluctor and not a 58 etc... Just a few ideas for you to check. GL.
Oh and the cam sensor and map have three wires. The sensors don't generally just go bad but can't rule it out. I didn't read you post above mine about the cam sensor, but I have seen it done so just double check. And the Tach won't move while cranking usually, but you can watch it on a Tech two or HP tuners etc.
Yeah more info. Same engine rebuilt? different engine. I did 408 swap in mine last fall.Cam sensor is three wires. I just went thru nightmare problem with mine. Finally found problem female connector was loose on a pin or pins?
Cam sensor won't stop the car from starting.It will start harder sometimes you have to turn key off then crank and repeat multiple times but car will start and run.
You can check easily for spark.hold plug against engine when cranking. You can check for fuel. Crank sensor will stop car from starting . Ok you said no fuel and no spark.
Are all injector and fuel related fuses ok. What pump setup..home made? Can't help you if its homemade setup. You have make sure your pumps are working. I went lonnies twin pumps,prewired and plug and play.Test your pumps if you can. Into a bucket.
Car should fire if you have fuel and spark. And crank sensor is plugged in and working.
for spark check main injector harnesses are plugged in and all related fuses are fine.
Engines are simple really give them fuel and spark and they run basically.
Are you getting any codes..you would likely get codes for crank sensor. I am betting you just aren't getting fuel to the injectors.But of course you need spark as well.
Cam sensor won't stop the car from starting.It will start harder sometimes you have to turn key off then crank and repeat multiple times but car will start and run.
You can check easily for spark.hold plug against engine when cranking. You can check for fuel. Crank sensor will stop car from starting . Ok you said no fuel and no spark.
Are all injector and fuel related fuses ok. What pump setup..home made? Can't help you if its homemade setup. You have make sure your pumps are working. I went lonnies twin pumps,prewired and plug and play.Test your pumps if you can. Into a bucket.
Car should fire if you have fuel and spark. And crank sensor is plugged in and working.
for spark check main injector harnesses are plugged in and all related fuses are fine.
Engines are simple really give them fuel and spark and they run basically.
Are you getting any codes..you would likely get codes for crank sensor. I am betting you just aren't getting fuel to the injectors.But of course you need spark as well.
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It's a rebuilt ls1 engine, still on stock crank. I did check the ground on the back of the driver's side cylinder head, along with double checking the harness connectors for the coils and all the fuses. It's a twin external walbro fuel pumps/braided lines and I ran a separate wiring harness for each pumps. Fuel pumps ARE WORKING and BUILDS-UP pressure when I turn the key on. And like I mentioned before, I already checked for any sparks from the spark plugs and did'nt see any, and the spark plugs are bone dry...no signs of fuel from the injectors. So, I guess I could rule-out the cam sensor, co'z it won't start at all no matter how many times I crank it, not even a slight hint of wanting to start. It seems like the crank sensor's plug is still attached, it's kind'a hard to see due to a heat shield blanket wrapped around the stater, but I might have to drop the starter and check the crank sensor later, I'm just out of time and won't be able to get to it again untill next friday..., I'm leaving tonight and will be out of town for the rest of the week, that's why I was really dissapointed and so bumed-out that I couldn't get it running before I leave, but thanks for all your responses, they atleast gave me some hope and somewhat narrowed it down as to where to start when I get back. Thanks, again!
, I'm leaving tonight and will be out of town for the rest of the week, that's why I was really dissapointed and so bumed-out that I couldn't get it running before I leave, but thanks for all your responses, they atleast gave me some hope and somewhat narrowed it down as to where to start when I get back. Thanks, again! Last edited by Boo"SS"t; May 31, 2009 at 06:36 PM.
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8 sec potential, 12 sec slip
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Definitely check the crank position sensor! That'd be my first guess from what you have said. Just gotta take the starter off to get to it- 2 bolts and a couple wires to disconnect.. Shouldnt be a biggie at all 
Since the other stuff I was going to say has already been mentioned. When I didn't get spark one time and it was because my ignition relay went bad. You can swap your fan#2 relay to your ignition relay just to eliminate that.
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I might just do that first, but what I'm wondering about is that a crank sensor or ignition problems could cause the fuel injectors to not spray any fuel during cranking??? I'm just still puzzled why the spark plugs don't show any signs of fuel.
I had that relay go bad on me too. It started doing it here and there and then finally died. The funny thing was that it would start if I jumped it but not on it's own. I think that relay controls fuel and spark.
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Ok, I just tried switching the fan#2's relay with the ignition's and still won't start, I then took-off and visually checked the crank sensor and wiring connectors everything looks fine, but still won't start, it would just crank and crank.....
. Well have you checked your PCM? If you have fuel to the injectors, but they are not firing and you don't have spark and your 100% on your wiring that would be my next check. GL!
You need to get multimeter and start checking power to things. You need to double check every fuse in the car. Are the plugs i properly in the computer. Take them out and reseat them . injector plugs are plugged in. you have fuel to the rail? Unlikely crank sensor just went all of a sudden. Maybe you crushed or cut some wires or pulled something out. Electrical problems can be so annoying!
Keep us posted. I had cam sensor problem that drove me crazy. Changed out sensor like three times. No way to bench test the cam sensor. Finally figured out how to check them in car with the car cranking intake still off. But every time had power to the sensor connector ,but sensor was intermittent. Turned out female connector was not grabbing pin tight. Had hard time plugging in the cam sensor when did my 408 swap. So it must have got opened a bit too much and intermittent drove me nuts. Cam sensor codes, car was hard to start, tach was dead as doornail well usually sometimes it was working.Finally took connector apart and tightened it up and no problems since.
So really you likely need a meter and start checking power here and there.
Keep us posted. I had cam sensor problem that drove me crazy. Changed out sensor like three times. No way to bench test the cam sensor. Finally figured out how to check them in car with the car cranking intake still off. But every time had power to the sensor connector ,but sensor was intermittent. Turned out female connector was not grabbing pin tight. Had hard time plugging in the cam sensor when did my 408 swap. So it must have got opened a bit too much and intermittent drove me nuts. Cam sensor codes, car was hard to start, tach was dead as doornail well usually sometimes it was working.Finally took connector apart and tightened it up and no problems since.
So really you likely need a meter and start checking power here and there.
I had a similar problem once. My problem was the MAP adaptor harness I bought for the 3 bar sensor was wired wrong. I swapped around the 2 outside wires and she fired right up.
OK, riddle me this, did you happen to have a 2 bar map and a 1 bar tune?
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Well, I did a little bit of search on it but nothing really helps. I finally finished installing the engine back into the car, and finished my new wiring harness for the dual external fuel pumps, I tried to fire her up but it would just crank and crank but won't start. I already doubled checked all the wiring harness, fuses, sensors and no luck. I then pulled the #1 plug wire to see if there's any spark while cranking...nothing, no spark at all. I then pulled a couple of the new spark plugs to see if there's any sign that the injectors were spraying...but plugs are bone dry. Needless to say, I'm really frustrated and bumed-out. I'm just about ready to give-up on this and throw this stupid car away.... I'd really appreciate any help as to what could cause this. Thanks!
. I'd really appreciate any help as to what could cause this. Thanks! I thought the ground was already mentioned, which is a common problem after the heads have been removed. It also happens if it isn't a good ground, ie frayed strap.