5.7 starting issues

[woody367]

So my 99 Yukon 5.7 has starting issues. Not like the other post list now. It will run fine for a week and then won't start. Fuel pump runs. Right now it has been dead for 5 days. I try to start it and cranks fine then it pops out the exhaust and at times the trottle body. There are no codes coming up. Could it be a crank sensor going bad? Anyway I can test the sensor? Thanks

 

[woody367]

Cam sensor? I do not know where to start or don't want just to throw money at it. I have a ACTRON CP9175 code tool. Not sure if it cane do live sendor testing.

 

[exp500]

Tools needed- cheap scanner, fuel pressure guage with long hose, multimeter, test light, spark tester. Less than $100. Otherwise keep throwing parts at it, as last post you needed a fuel pump. If you are willing to test it, we are willing to assist in finding your issue(s).
Don't think of it as OH Shit another $100! Figure what a replacement truck will cost and for less than 1 payment your truck is reliable again. Do it right.

 

[woody367]

Thank you. I got everything together just need to get the fuel guage. I willn check spark and pressures by Saturday. I almost sound like timing is off, But will check.

 

[willxfs]

An easy thing to check is the distributor cap. They are know to get corrosion build up on the contacts on the inside. My 1998 tahoe did that and it wouldn't start and would hardly crank due to the timing being all jacked up due to cross fire within the cap. If the other tests mentioned in the post above don't resolve the problem, you could pull your distributor and check the gear on the bottom. It is known to thin out and become knife edged. Just be sure to mark the distributor location on the manifold and the position of the rotor pointer on the distributor. Good luck and keep us posted.

 

[OR VietVet]

How old are all the ignition related components? Cap, rotor, plugs, wires? Yes, check the drive gear and look all over when the cap is off. May have moisture in cap. Yes, get a fuel pressure reading and if starts, pressure at idle and rev engine and while driving if can. How old is the pump? Old is the filter?

 

[woody367]

Thanks guys, went out and it started right uo, bo issues . I will pull the cap and check inside. AAll the ignition parts are a year or so old and all ADelco. Fuel is a week old, Fuel punp is about 7 years old.

 

[OR VietVet]

When you open up the cap, take some pics of it, the rotor and the inside of the distributor. Have seen some nasty pics of inside the distributors lately on the forum.

 

[FAT TRUCK OWNER]

I JUST WENT THROUGH IT JUST LIKE YOU. FIRST I CHANGED CAM SENSOR THEN CAP & ROTOR AND I CHECKED INTAKE MANIFOLD GASKET . IT BLEW OUT FROM INTAKE COVER. SO I CHANGED THAT ALSO. SINCE I GOT POP SOUND FROM THROTTLE BODY. GOOD LUCK ALSO I CHANGED PLUGS AND WIRES

 

[woody367]

Well went out to check fuel pressure , spark and dist. cap. My hands are so cold I can not evern get the pressure gauge screwed on. I will have to wait till it is a little warmer out or it starts and can put it in a warm garage. I am getting old I guess. LOL

 

[exp500]

Thanks for update. Keep them coming!

 

[woody367]

I have spark, and fuel pressure is 58 psi and drops to 52 when relay clicks off. I will pull the cap and rotor in a day or two just to check it. It is suppose to rain tomarrow.

 

[exp500]

Woody367- I have been following both of your threads, so to not confuse me or anyone else, do not start any more and we will get you going and finish any other questions here.
What I need from you is All your vehicle specifics, maintenence history and results of prior work.
For fuel pressure, 1) test at key on engine off, 2)cycle key 3-4 times to on to see if pressure rises above 1).
3) engine idling 4) driving 5) time on leak down when key off. Asking for more because I've seen only one of this vintage runs at 58#, One wouldn't run at #61.(same guage).

 

[woody367]

Woody367- I have been following both of your threads, so to not confuse me or anyone else, do not start any more and we will get you going and finish any other questions here.
What I need from you is All your vehicle specifics, maintenence history and results of prior work.
For fuel pressure, 1) test at key on engine off, 2)cycle key 3-4 times to on to see if pressure rises above 1).3) engine idling 4) driving 5) time on leak down when key off. Asking for more because I've seen only one of this vintage runs at 58#, One wouldn't run at #61.(same guage).

I only have one post going about this. It will not run now so that is the only fuel pressures I can get.Today iy backfired out the TBI with lots of smoke. I sure sounds like timing is off. I pulled the cap and rotor and they look almost new. I have a new set on the shelf so I will just change it. Mot that I want to throw money at it I think I will replace the cam sensor while the cap is off. I like to use OE parts but can not get a ACDELCO sensor for a few days so I will just pick on up from advanced auto. The truck has 180K on it. Always maintained but have never do a cam or crank sensor. I have put 2 fuel pumps in it in the past. I rechecked and there are no code found.

 

[OR VietVet]

Smart move while you are in there.

 

[exp500]

Woody367- your present situation with backfireing with no codes sounds like distributor cap. Check wires inside dist. they sometimes wear rubbing on dist deck.
Does your tach needle bounce around while cranking/backfiring? (meaning outside of range expected/not stable). Usually bad cam sensor shows as P1351 or others.
What are you using as scanner? Also check plug wires at correct cylinder.

 

[woody367]

I am going to change cap, rotor and cam sensor while it is apart. I will check all the wires also. No sure about the tack, I was not looking. I have a ACTRON CP9175 code reader. Thanks

 

[1BADI5]

I had this same problem back in '18 with my 99 Yukon

It was the crank sensor

 

[woody367]

That will be my next try. I need this thing back on the road.

 

[exp500]

Yes you can test crank sensor- but you have spark so no test. Thats why I asked about Tach bouncing.. Sometimes the pigtail for the crank sensor gets wonky, just like the one for ICM. Usually test those on a missing/sometimes dies engine with engine running.
Next step after cap/rotor if no start is spark test at Dist coil term/ then at coil. A 5 second crank is good if you can see it well. Report if uneven or weak spark.