93 6.5 starting trouble

[Evan Adams]

I posted awhile back about my truck not wanting to start. Well shortly after that it started doing it again well i went and bought and ops and a new lift pump from ac delco. Well now it has fuel pressure and will turn over but wont start. I have just about given up so any help is wanted. Im hoping its not the mechanical injection pump and was wandering if it could be the pump timing or something please help.

 

[towcat]

these motors are notorious for airlocks.
first, loosen the nut on the output side of the secondary filter and crank the motor. you should see fuel coming out. if not crank for a while longer to clear out the air.
next make sure you have 12v to the fss on the injection pump.
last, loosen up an injector nut where the line terminates on the injector. crank for a bit. you should see fuel.
if not, your pump is ******.

 

[tanman_2006]

When you turn the key to the on position you should here the FSS click too. Bleed air as said. Sometimes alternative fuel useage can cew up the pump internals and lock the pump which leads to a snapped pump drive shaft, high miles can do this too.

 

[Evan Adams]

Well last night after it had cooled off i went out to roll up the windows and i said lets try one more time. Well it started. And i was thinking back to driving it and after it got warmed up the glow plug light stopped coming on and when i would shut it off the lift pump wouldnt run for a little afterwards. So i think i have a wiring problem somewhere. Also when i bought it the glow plug light came on no matter what and the lift pump didnt work but it does now that i got a new pump and ops. but it runs after you turn the truck off is that normal? and do these motors start off primarly compression or do the glow plugs help with that. Because our duramax's injectors heat up to help it light of in the beginning

 

[towcat]

Well last night after it had cooled off i went out to roll up the windows and i said lets try one more time. Well it started. And i was thinking back to driving it and after it got warmed up the glow plug light stopped coming on and when i would shut it off the lift pump wouldnt run for a little afterwards. So i think i have a wiring problem somewhere. Also when i bought it the glow plug light came on no matter what and the lift pump didnt work but it does now that i got a new pump and ops. but it runs after you turn the truck off is that normal? and do these motors start off primarly compression or do the glow plugs help with that. Because our duramax's injectors heat up to help it light of in the beginning

how warm is it where you're at?

 

[tanman_2006]

Well last night after it had cooled off i went out to roll up the windows and i said lets try one more time. Well it started. And i was thinking back to driving it and after it got warmed up the glow plug light stopped coming on and when i would shut it off the lift pump wouldnt run for a little afterwards. So i think i have a wiring problem somewhere. Also when i bought it the glow plug light came on no matter what and the lift pump didnt work but it does now that i got a new pump and ops. but it runs after you turn the truck off is that normal? and do these motors start off primarly compression or do the glow plugs help with that. Because our duramax's injectors heat up to help it light of in the beginning

Lift pump runs as long as there is oil pressure it takes a few seconds for it to bleed off.

The 6.5's have high enough compression that they should light in over 60-70*F weather w/o much glow time. Mine will light w/ ~5sec of cranking no glows. Takes a healthy starter, batts, and good cables.

 

[Evan Adams]

its like high 70s 80s but the light stays on for probly 15 sec or so and then it will kick on and off for about 2mins after you start it. so i think there is a electrical problem because also when it warms up the glow plug light doesnt come on the the lift pump doesnt activate. Also the motor runs really cool like 180 degrees or a little more but never up to 210 area ever even when its super hot outside and you driver it alot. Idk im so lost on it now.

 

[tanman_2006]

its like high 70s 80s but the light stays on for probly 15 sec or so and then it will kick on and off for about 2mins after you start it. so i think there is a electrical problem because also when it warms up the glow plug light doesnt come on the the lift pump doesnt activate. Also the motor runs really cool like 180 degrees or a little more but never up to 210 area ever even when its super hot outside and you driver it alot. Idk im so lost on it now.

There is a wiring problem somewhere if you replaced the ops and LP already. I thought you said the LP runs after shut down? Start by checking, cleaning, and tightening ALL grounds.

Glow plugs should be on for 8-12 sec. 91-93 6.5's have temp controled GP controlers, when the engine is cool it could be on for 8-12 sec but when hot could just flash on then off.

Someone could have installed the wrong t-stat or your temp gauge is off. You need to use a IR Temp Gun on the thermo housing to varify the temp before digging at a problem that isnt there.

Air leaks can cause hard starting and if the in-tank sock is dirty then you wont beable to pull enough fuel to start or run very well.

 

[Evan Adams]

yes its runs but only if the glow plugs turn on when starting. Yes i believe the gauge is off but it might not be the tstat as most of my gauges are off already. (20 oil press when off, on battery power when key is on, negative mph, fuel gauge off by 1/4 of a tank, trip miles doesnt work. But it has 231k almost 232k and use to be a state highway truck. also when you drive the truck for a while and you go to open the fuel tank cap there is pressure. is that a sign of an air leak?

 

[Evan Adams]

and it might be a sock filter but it runs like a champ when its running.

 

[Evan Adams]

also could it be the glow plugs as they are original with 231k miles and they are 20 years old i have already replaced the glow plug relay with the correct 4 poll.

 

[tanman_2006]

also when you drive the truck for a while and you go to open the fuel tank cap there is pressure. is that a sign of an air leak?

You have the wrong fuel cap. Your tank is pulling a vaccum, thats not helping your issue. Been there done that, I just busted out the spring and valve in the center of my cap so I dont have to worry about it happening again. Next time it wont start try unscrewing your fuel cap to release the vaccum.

I will try to find you a wiring diagram for the glows and lift pump. I am betting your Injectors are weak enough that you arent atomizing fuel good enough to start w/o glows.

You need to check and see if you are getting power to the glows, its a 12v system. Might be time to change the glows if they were coming on while running, that will fry them quick, BUT before you put new ones in you need to make sure your wiring is straightened out.

The LP has key on power, it shouldnt be connected to the glows in any way UNLESS someone tried to wire it to "prime" itself while the glows were on for easier starting. That is a common mod for 6.5er's but I doubt a Gov mechanic would do it.

 

[Evan Adams]

ok thankyou if you can find a wiring diagram that would be great! i will fix the fuel cap tomorrow. Sorry for the late reply my internet was down. Ill get a voltmeter and check glows and lp. I plan on getting new glows also as they are just about shot i personally dont think they work. And injectors are on my list to get get bosch marine injectors with the bigger nozzles. Also here in indiana i wouldnt doubt the wiring thing as they already bondo'd the cab corners and the front fenders and the bed which i had to replace all of that except the cab which i left because your cant tell unless you use a magnet. And they arent gov workers they were county highway workers so yeah.

 

[tanman_2006]

ok thankyou if you can find a wiring diagram that would be great! i will fix the fuel cap tomorrow. Sorry for the late reply my internet was down. Ill get a voltmeter and check glows and lp. I plan on getting new glows also as they are just about shot i personally dont think they work. And injectors are on my list to get get bosch marine injectors with the bigger nozzles. Also here in indiana i wouldnt doubt the wiring thing as they already bondo'd the cab corners and the front fenders and the bed which i had to replace all of that except the cab which i left because your cant tell unless you use a magnet. And they arent gov workers they were county highway workers so yeah.

County highway isnt any better lol.

Marine nozzles arent worth the coin. Just have Mel build you a set of Bosch Germany injectors set at 2300psi. Marine is exactly what the name implies, good for marine engines that stay at WOT all the time. Trucks shift out before they see any advantage to the marine nozzles.

LP and OPS operation Didnt check and see if it had wiring ay out but it might help.

Ground locations

I'll try to keep scratching on the 93 glows. I just rewired my whole 93's glow system and added bigger wires throughout. I could try to walk you through it but I suck at explaining wiring, I would prefer to find an article or explanation from someone else.

 

[Evan Adams]

ok how much does mel charge and where is he located?

I will look into it today and see what i can find