I am the owner of a 1986 F-250 6.9L. Heres the deal. The truck will not start, when I plug the block heater in, then it will. So do I immidiatley think glow plugs? Yes. We replaced the plugs and the relay in hopes that it would fix it, well it didn't. The wait light still cycles correctly or so i think, and i can hear the solenoid clicking on and off when the light turns on or off. It smokes when cranking so, I think i can rule out a fuel problem, and when it does start, it runs well and i can see initial smoking stop when the wait light is on, after it's running in the mirror. It does smoke lightly though until it warms up for a minute or so. How can I tell how much power is going to the plugs? Any help would be appreciated.

 

when you replaced the glow plugs did you do a compression check? higher mileage engines won't start real easy. also make sure that both batteries are in good condition along with starting system. if engine isn't cranking fast enough it won't start. if the glow plugs were hard coming out did you clean the bore or port where they screw into the head? if you are in really cold weather you may need to cycle the ignition 2-3 times also. since you already replaced plugs and relay which is right way to go i would not worry about how much voltage is going to the plugs because it sounds like the system is working properly. as long as the harness is in decent shape you should be getting the right amount of voltage. but if you want to check it just have a friend help you and a multimeter. disconnect one plug and put one lead from multimeter to harness connector and the other lead to ground. then have friend turn key on and observe voltage. i can't remember what voltage reading should be. but if all of the above checks out. check fuel quality and if that is ok then it may be time for injectors and pump.

 

The plugs came out and went in easily. It is a higher mileage engine 180000+, so i could do that, but would that result in no start at all? I have kicked it with ether. The batteries I am going to change anyways because they are as old as the time we have had the truck which is roughly three years, the starter turns the engine over, but i might get a new one, better now than in the iddle of no where, god knows how old it is. The fuel is new and fresh, and we have never had a contamination problem before. I talked to a ford diesel mechanic, and he said that if the ip was going bad, that the truck would not run at all, so do you mean the low pressure fuel pump? Weather ain't a prob, it was 63 degrees when I tried to start it here in chi town.

 

Have you actually checked for voltage at the glow plug connectors? Still sounds like no/low power to GP system. My 93 has 205K on her and fires right up in 5 degree weather.

 

I have not actually checked the voltage. What is the basic procedure? And if i find it is not enough, what could be the culprit?

 

i have an 87 f250 w/ 6.9 myself. also have 95 f350 ps. they both have over 250k on them. the 87 had the same problem and i went the same route and ended up being injectors. if you want to check voltage at glow plug connectors and don't have multimeter you could use a test light (kinda half assed way) but if the light is bright when the key is turned on you most likely have plenty of voltage. if you have that many miles on the engine and the injectors are original, i would venture to say that is the problem. you can take the injector lines loose and crank it over to check fuel pump volume. the springs in the injectors wear out after so many miles or usage. the tips get clogged with carbon as well as the ports for the glow plugs. but before you go buying anything i would check voltage at glow plug conns, then remove a few of the glow plugs and look down in the port or fish a coat hanger down in the port to ensure they are not packed with carbon. then check fuel pressure or volume, if you don't have a pressure gage then remove the supply hose from the low pressure pump to the ip and put end in a bottle and have someone crank engine. should have pretty good stream of fuel, then check fuel flow at the injectors by loosening the line fittings and crank engine. should be good flow. then you can remove injectors and reconnect fittings to them and crank engine and observe spray. should be a really good spray pattern. if any drip or don't spray really strong. they will need to be replaced. let me know if you need any more info. just remembered there is a connector on the passenger side of the engine compartment right on the fender well. check that for corrosion.common problem

 

RLord4268,
Look on the passenger side of the motor near the dip stick. Look for the engine wiring harness where it comes over to plug into the chassis harness. There is a connector that is off white in color.
You will see two orange large wires on one end of the connector. The large orange wires are the glow plug power.
Inspect it very carefully for signs of overheating or melting on the end with the orange wires.

If it looks OK then unplug the connector and check for corrosion on the terminals.

Mine melted a couple of years back and the glow plugs were getting only partial power.
To fix it I cut both orange wires on each side of the connector as close to it as I could. Strip each wire 1/2" and put them all in a copper split bolt (electrical supply house will have them, it has to be sized for 4 #10 AWG wires) Then tape it up real good so it don't short out.

All the other connections in it were OK, just the glow plug side was affected.

 

yeah, that is a common problem. don't doubt you there.

 

have u checked your air filter