have G-P starting issues. realy wires plugs and all seem OK. if I jump across the GPR and slowly count to 5, then try to start, all is fine.

trying key, unit IMMEDIATELY goes to rapid cycling the plugs. maybe 1 or 2 seconds of heating then cycling. all plugs have resistance less than 0.5 ohms (and now, each wire has been on and off so contact should be clean).

I suspect resistance through relay may be issue, plan to measure the voltage drop when active.

however, I have not found ANY INFO on the controller. apparently, it grounds the GPR for a length of time dependent on temperature, then moves to a cycling regime. where is that temp meausered? who has a time versus temp chart? is there a duty cycle for post heat published somewhere so we know it is doing what was intended? it is NOT the coolant switch up front--that only controls fuel timing and fuel heater and something else (there are diagrams for that posted everywhere). or am I wrong and there is temp signal somehow getting into the GPR controller?

for now, I plan to pigtail a wire out from under air cleaner so my customer can "hold this to ground for 10 seconds" before starting. I have heard this GP system rarely needs this trick but I don't want to throw parts at it until I can test the GPR controller. or if they are cheap, just swap it.

anyone know how to test the GPR controller? how much do they cost? are some relays at parts stores really expensive because they have a controller with them?

I will also check the ground wire for the GPR and stuff next time I am in there...

thanks!!!

 

oh yeah:

92 F-450 7.3 IDI

 

not quite like I thought. I manually grounded the GPR for various time periods today. on arival, tried to start, rapid cycling of GPR. Grounded to energize for about 10 sec (temp is 40F or less, light snow, none sticking to ground). no start but light firing. grounded for another 15 sec and it started up. As a test, customer immediately shut down so we could try a restart. it did not start after that.
HOWEVER
the GPR behaves as expected now!!! key on, one click, light stays on a while, GPR stays engaged for a while. light goes off after maybe 15 sec and GPR never goes into the cycling thing anymore. BUT truck won't start.
we tried grounding GPR for up to about 30 seconds after WTS light went out to keep heating, but nothing.
i am guilty of forgetting one thing--i forgot to check the ground wires at GPR area.

any ideas? anyone know how to check the GPR controller?
thanks!

 

I don't know how to test the controller itself, but I can tell you a few things that may or may not help you at all:

1) the controller measures the resistance of the glowplugs circuit somehow, not the temperature of the engine - my controller would energize the glowplugs for at least 5 seconds even when the engine's been just shut down after several hours of run time. Hot glowplugs have higher resistance than cold plugs, hence why with the engine cold the controller glows them for over 15 seconds, but when they're as hot as the engine to begin with it only keeps them on for a few seconds. The higher the resistance the shorter the glow cycle.

2) there's only one ground for the system, a thin black wire coming from the back of the controller and going to one of the intake plenum bolts. The condition of this ground can affect the length of the glow cycles - a bad ground causes the controller to keep the plugs on longer. In rare situations you can have both a few burned out plugs, and a bad ground, these two cancel each other and the controller glows the remaining plugs as long as it used to do all 8, but there will be a hard start condition.

3) at 45F my truck can fire up only on 5 glowplugs energized for 10 seconds - which is why I have a manual switch like you described installed in my truck, so I can override the controller should I lose a few plugs without having the option of replacing them right away.

4) the factory wires that carry the current from the battery to the relay are pathetic - you have two 10-gauge wires, each subjected to 100 amps of current. To remedy this I've added a 4-gauge power cable to the system, it runs from the battery to the relay directly, and as a result of this my glow cycles have shortened by a few seconds and truck starts easier and smoother even without engaging the high idle.

5) the factory "wait to start" light is an idiot light, it's operated by the controller and does not indicated the actual operational state (on or off) of the glowplugs relay.

In your case I'd suggest that you inspect both the ground connection for the controller, and the big engine harness plug on the passenger side of the engine bay as that's where the relay power wires go through and said plug is known for deteriorating and restricting power delivered to the relay. In respect of my observation #5, I suggest a bit of wiring modifications - on the back of the controller locate a blue wire with a connector on it (there's only one, so it won't be hard to find), snip the wire off right against the controller's body, then add a small ring terminal to the now-loose end of the wire, and connect the ring terminal to the small post on top of the relay where the small white wire is (same post you're grounding to test relay operation) - this makes the light glow only when the relay is powered up, so you and your customer will have more accurate information on when exactly the relay energizes and for how long it powers the glowplugs. Also, while you're at it, do indeed run a wire from that same post of the relay to a good ground inside the cab - use a momentary switch (only makes connection when it's held on by your customer) in that circuit and install it somewhere on the dash where your customer can easily reach it - flip the switch (or push its button) and the glowplugs will work for as long as you hold the switch, no matter what the controller has to say about it. Offer the customer to upgrade the power feed wires for the relay, they may or may not go for it, but it's an upgraded these systems could have used even when brand new and in top condition.

All this said, have you checked resistance of each and every glowplug again AFTER you did all the testing at the relay? It really sounds like you cooked them in the testing process, but at the same time a bad ground at the controller prevents it from detecting this, resulting in the situation described in my #2 observation...

 

any that weren't cooked before I got there are finished now.
they were the 5V autolite plugs, not 9 or 12 V like I expected.
That may explain the more-rapid-than expected cycling.
I got them all out easily, like they hadn't been in there very long.
will be shopping for motorcraft brand plugs, and need to confirm we should use the 5V plugs. Who would know? I have the VIN if that helps. I will call the dealer now.
I also measured them wrong the first time through--it was dark and I couldn't see that the hex shell is actually quite thin--i measured the resistance of my meter leads only, and about a half inch of the nickel plated bullet tip (the nickel is the reason the resistance was believable and not showing as zero).

this is navistar 7.3 family 185 non turbo. Ford made vehicle in canada in 5/1992 sold incomplete and someone put a dump-box body on it.

 

dealer gave me a big long number F4TZ12A342BA which googling causes the suggestion that this is ZD-11

most others, including an autoparts store that has the motorcraft says ZD-9

I suspect this is my 5V versus 9 or 12V dilema.

need to know which plug this GP system expects to find. Were the autolite 5V plugs i found there incorrect?

anyone know? would Navistar know? are they still around?

 

is the dealer wrong?
the autolites i took out cross to ZD-9
everyone on these forums says ZD9
Sil-Terhar Ford in Broomfield Colorado quoted me ZD-11
autoparts stores say the ZD-11 is much longer.
What applications take the longer plugs? apparently, they fit 94 and later and turbo?
again, this is 7.3 navistar A185 non turbo from May 92.
did maybe someone replace with the wrong plugs?
Who KNOWS teses engines. i am getting reluctant to trust the dealer. I had him pull one and describe "bullets both ends and about 3 inches long" but i understand ZD-11 is actually longer?

 

Numberdummy, or one of the other parts guys on here, would be the best person to ask. The part number given to you by the dealer starts with F4... which in Ford part numbers indicates a 1994 part number. The reason I suggest Numberdummy is that 1. either Ford made your glow plug part number obselete and has replaced it with the newer part number. Or 2. That the dealer mistakenly gave you a part number for the 94+ turbo diesels rather than your NA application. Or 3. Ford obseleted your application glow plug with no replacement from Ford available and the dealer gave you the only one it knew Ford still lists.

 

two calls to dealer and they were wrong and lied about length. everyone here is correct--the F4xxxxxxx number which is ZD-11 part is for newer turbo diesels.

i called second dealer and confirmed ZD-9 is correct and then ran to checker and bought 8 at high $15 each price, but quickly got truck running normally with the allegedly best Beru german ZD-9 in Ford baggies..

THANKS EVERYONE!!!
FYI some of the autolite say 1108, but a few also have "5V" on them in addition to 1108. i am not sure whether this is a voltage spec or not at this time, and will probably never know...

the motorcraft/beru/ZD-9 looked far more serious and had a big string of german-style numbers made me think of bosch parts...lots of zeros and 1!

 

Actually Bosch do make plugs that fit the IDI engines - if you ever get another customer with a truck like that, do NOT use the Bosch plugs, the only thing that should go in an IDI is a Motorcraft/Beru plugs, ZD-1A for the '83-'86 6.9 engines, and ZD-9 for the '87 6.9s and the '88-'94 7.3s

 

for future reference autolite, champion wellman and all the other glow plugs are pure crap/ the only glow plugs to use in a ford are motorcraft/beru. ZD-1 for the 6.9, zd-9 for the IDI 7.3, and ZD-11 for the powerstroke.
next time you need glow plugs, try this site. he stocks all 3.

7.3 Liter Diesel Motorcraft Glow Plugs - Ford 7.3 Liter Diesel Motorcraft Glow Plug

 

Tom, actually I've had good luck with Wellmans, they lasted 2 years in my truck, and when a few finally burned out and warranted a new set of ZD9s they still came out with no fight needed.

 

yea, the wellman's don't swell the tips like the autolites do.
they just don't last like the M/B plugs so.
a buddy was putting the wellman's in his truck, and was getting about the same thing, two years from a set. he finally saw the light when he found out i got 14 years out of my original set of M/B's, and the second set has been in there for 7 tears, and are still working like i just put them in