Has spark fuel pressure and air but will not run?

pmelah

Original poster
Member
Jun 16, 2015
7
hey guys im new here and got a strange problem tat i cant figure out before this i did have a crank/cam p1345 i have spark and fuel pressure turns over fine but wont run i went to salvage yard to get some used sensors but could only find them for the 4.6 will that work on the 5.7? and wha would cause the motor to not run all of the sudden could it be the ignition switch im lost and need a direction to go in thanks


i forgot its a 99 suburban LS 5.7
 

MAY03LT

Member
Nov 18, 2011
3,412
Delmarva
Hey what happened with p1345? Is that related to the current crank/no start?

The most common things that I see on those engines for crank/no start are weak spark and low fuel pressure. The fuel pressure has to be between 60-66psi and the secondary ignition has to be able to jump a 30kv gap.
 

pmelah

Original poster
Member
Jun 16, 2015
7
it has a weak spark i pulled the crank sensor and cleaned it up i have 2 crank sensors from a 4.3 and was wondering if that would work on the 5.7 the bracket not the same or the sensor fuel pressure is up there i say that with no gauge it shoots the gas out of the shrader to the hood so i know it has good pressure but what would cause a weak spark it has a new coil on it plugs are 4 months old wires are 6 months but changed with plugs
 

littleblazer

Member
Jul 6, 2014
9,265
It still has a distributor correct? Check that, I've had new coils be junk right out of the box as well, granted this is on a boat motor, but it's still coil and distributor type setup, that the 5.7 had at that time if i remember correctly.
 

MAY03LT

Member
Nov 18, 2011
3,412
Delmarva
Usually weak spark is due to gunk in the distributor cap. I put a cheapie b/w d-cap on my pickup (also 5.7) and not even 6 months later I had no start/weak spark due to corrosion in the cap. Put a name brand on and 2-3 years later it's still going strong.
 
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pmelah

Original poster
Member
Jun 16, 2015
7
i think i stripped the head of the screw on the back side so hunting for something to get the screw out
 

pmelah

Original poster
Member
Jun 16, 2015
7
checked the cap and button cleaned them good just a little corrosion on it put every thing back together and now i have no spark checked the code reader and it is p0339 p0336 crank shaft position sensor weird because i had spark yesterday now i have nothing before this my tach had started acting funny showing 200 rpm when running at 45 mph it would show 300 rpm on the tach does the crank and cam sensor control the tack and coil for spark i figure the ecm has to be good since my scanner is reading codes
 

Mounce

Member
Mar 29, 2014
13,667
Tuscaloosa, AL
I'd probably replace the cap at this point and maybe the button too. You had spark until you cleaned them and now you don't have spark so one of them must've failed unless you didn't get it put back together just right.

Although, idk if the codes are related to your fail to run issue. I'm kinda thinking they're two separate issues.

I'm not very familiar with distributor driven ignition systems so if someone that is doesn't agree with my opinion please share. I'm just going off of the story and my opinion from my understanding of the system.
 

MAY03LT

Member
Nov 18, 2011
3,412
Delmarva
I'd start with p0336. At the crank sensor, the pink wire should be 12volts with the key on, purple is ground, and yellow should be 0-5 volts while cranking. Technically the yellow wire should be tested with a lab scope but there are ways to kinda cheat and use a dmm.
 

pmelah

Original poster
Member
Jun 16, 2015
7
to my coil i have one hot wire to the ignition control mod i have 2 hot wires both outer one each side this checked by test light i dont have a scope so im sol on that and cant take it to a shop unemployment does not offer the expenses to afford that lol went to a salvage yard and pulled the coil and mod off of a running 5.7 and no spark.... now several months ago i had a problem with the security light coming on and staying on when i was driving to and from work 4 miles one way then it quit doing that and would only come on at bulb check about 3 weeks ago it locked me out and would not start security light would not shut off and it would not start for 2 days then started working (about the time my tach started acting weird 200 rpm when my scanner read 600) now the security light comes on at bulb check and goes out like its suppose to and turns over but of course no start would or could the vats system have shut down the spark control as well as the injectors i have seen some strange things that are explainable over the years just throwing that out to scratch some heads all my fuses for ecm, crank, and ignition all have power key on in run and key on start i did get a pin out of the ecm and plan to check that today and will try to find a wire diagram
 

gmcman

Member
Dec 12, 2011
4,656
Have you checked all your battery connections? Almost sounds like when you drive around on the alternator alone and things get real quirky. If the battery has poor connections, including the grounding points on the frame and engine...you will generally not get a low battery symbol since the alternator is supplying sufficient voltage.
 

gmcman

Member
Dec 12, 2011
4,656
With what the others said, you definately need to ensure you have a good crank trigger. If you're throwing a crank sensor code and it's not running, we must ensure the crank sensor is working. I had a crank sensor go bad and it would run, then shut off on the highway, after 10 min I could restart and drive a mile or 2 until it crapped out again.

Check the spark at the coil lead, then compare it to the spark at the end of the plug wire....is the spark weak throughout?
 

pmelah

Original poster
Member
Jun 16, 2015
7
hope everyone had a good 4th of July i had not messed with the suburban since the 27th replaced the ignition wire harness crank sensor ignition module next to the coil all used parts from pull a part in New Orleans i took the key cylinder out and cleaned it up really good and sprayed some deep creep in it works almost like brand new i now have a good bright blue spark i hear the fuel pump kick on it cranks but does not run i can cycle the key 5 or 6 times and she tries to start then just spins i have the 3 needed spark fuel (just don't know what pressure) and air i do smell gas when i try to crank it and she try's to hit the one time but that's all i am suspecting the regulator or no power to the injectors not sure the smell of gas is short period and only when she try's to fire then its gone she does have a stumble in it when trying to crank it to she never had that before im at a loss and need to get it running since it is my only transportation at this time any helpful ideas on what to check would be great oh and it does not have any codes listed in the computer since i changed the crank sensor



think i found the problem after messing with the distributor i think it has jumped time got it close a couple times where she almost fired up but could not get it right so looks like a new timing chain and gears in the future last ime did the chain and gears i only changed the cam gear and chain due to not getting the crank gear off and the fact it has over 300k on the clock first time i did this it had 125k on the clock
 

Mounce

Member
Mar 29, 2014
13,667
Tuscaloosa, AL
I'd verify fuel pressure. Do a leak down test while you're at it, might have a bad injector spider leaking (I've heard of them going bad before) the pressure and flooding the engine. That'd explain fuel smell when turning key on.

Other than renting a pressure gauge, to rule out leaking injectors flooding the engine, put the gas pedal all the way to the floor and try to start it a few times. Putting the pedal to the floor cuts off fuel and will clear the flooding if there is one.

If it starts while holding the pedal to the floor, you'll get to have the fun of pulling the intake to allow you to replace the spider injector assembly.
 

gmcman

Member
Dec 12, 2011
4,656
Are you sure you have the plug wires on the right post? I'll go out on a limb and say it's unlikely it jumped time. Bump the engine until you have the timing mark at 0 and verify #1 is at TDC, then check rotor position. Hopefully it has a timing marker.

If the plugs are fuel fouled then you may need to trash them, at least try to clean the electrode.
 

Mike w

Member
Jun 24, 2014
287
It seems like an issue with the passlock to me. is the security light on? if not the rotor button screw could be broken



61YQqe0ft-L._SL1500_.jpg make sure both screw holes shown have screws
 

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