i am new to FTE but have been following your guys forums for quite some time and i am impressed by how much i have learned about my truck but still have one issue. i have a 1990 f250 7.3L and the wait to start light only comes on 2 seconds MAX. and i have heard that it is the relays way of telling you glow plugs are bad but i have perfect starts everytime despite rough runninh at first due to air intrusion. is this something i should be concerned about?

 

More than likely the rough starts are from a couple burnt out plugs, however the ones that are still working are getting the job done.

 

Check your glow plugs, and I bet you will find at least one plug that is bad. As Hairy said, the rest are getting you started, but it is not firing on the bad plug cylinders.

 

thank you for the help, i will check plugs tomorrow but do you think glow plugs are the cause of rough running at start up? it sounds like the engine doesnt get enough fuel at start up. and i was under the impression that this was caused by air getting into the fuel system. it is only the first start of the day and maybe if it sits for 5 or 6 hrs. also ifthe light only comes on for 2s then shuts off has the warming of the plugs been completed or should i wait another 6-8s for it to be the normal 8-10s cycle for the system?

 

I would say the plugs have a lot to do with the ruff running at start up. With air intrusion, a lot of times the truck will start, run for 1-2 sec., then die with an extended cranking to get it to start up again. The GP controler operates on reading resistance from the GPs. When a couple of GP are bad, the controler sees a different resistance, so it short cycles. It will do no good the wait the extra time if the wait to start light is out, it will only let the good plugs cool down.

 

yes, the truck will have a tough time starting and stumble.

it may start good now but in the cold it will be a PITA to get to start with bad gp's.

 

when i do start it, it does wanna just fall on its face and die i have to keep foot on gas for a good 30s but after that it runs perfect. and thank you for the info on glow plugs i am going to just go buy a few new beru plugs and see if i can find the ones that are bad.

 

thats definitlely air intrusion....

 

i have replaced all return line caps, o-rings and hoses and nothing is leaking there. i do howver sometimes smell fuel but have no idea where from and cant see any

 

and/or bad plugs. i had 4 bad plugs and what the OP is describing about his starts is the EXACT same thing mine was doing. i ONLY replaced the plugs with Beru and the truck started great and no more smoke or need to stay on the throttle to keep it running. BTW with the bad plugs i could smoke out the parking lot at my school with white smoke.

 

thanks for the info i guess i will just go ahead and replace all the plugs and hope that solves it because it is a real pain to get started especially if you let it die.

 

It is starting to sound like you may have air getting in and bad plugs. I would check your plugs first to make sure that it is plugs and not the controller. Heres what i did to check for air on my dads truck when we were having issues. We had a full supply of fittings and hose at our shop on the farm, may not be as easy but this is what we did. Stick some clear hose (we used sprayer hose) from top of lift pump / FF head hard line to FF head. Fired it up and bled all the air and shut it off. Within 3-5 minutes we could see very small bubbles coming up from the lift pump, turns out it was letting air in, and lettting fuel drain back. About a month later we were getting air from the o-rings in the hard plastic lines from the tanks to the switch valve, however we suspect that was due to an accidental use of brake fluid instead of power service lol.

Just to add, we also did o-rings, caps and return lines first, and while it helped, didnt wholly solve the problem until we changed the lift pump.

So now my question. When you start it cold and have to keep it running, does it just run rough and stumble, or does it surge and rev by itself?

 

when i start it it just stumbles and runs rough i have never had it surge or rev by itself, however i did check all of my glow plugs today not a single one was bad they all read .8 ohms. so if its not plugs then what is it? just air intrusion? is their any basic test to check for this without changing out all of my fuel lines for clear tubing?

 

are the plugs getting power when the key is in the on position?

Glow plug diag info

 

i will test tonight but i would assume so since the light comes on and i have after glow click. what should plugs read power wise? and how can i test if they have power?