bought a new relay that has 4 posts, my 97 350's relay has 3 posts. continue looking for new relay....?

 

Typically the G/P relay has 4 posts. Two large posts ( bat pwr input, G/P pwr output) and two smaller posts ( pwr and ground). A relay is uses a small current to controll a larger current.

 

thanks for the reply. napa and another parts store both come up with one with 4 posts. dealers has 4 posts ($98, by the way). mine has 3 posts...really. am i missing something here?

 

Where is the relay at? They may be using the case as the ground, although I have not seen this before.

 

well, bare with me here. i figure it's that selenoid looking unit with the wires coming from the battery and leading to the valve cover. it's mounted to the inside of the passenger side fender close to the battery. it's mounted to metal. ...while we're at it.. after reading previous posts, i'm trying this before i look towards replacing the glowplugs. won't fire up in the cold, yet starts just fine when it's plugged in. ...?

 

My truck is from the previous body style, but my glow plug relay is mounted directly above the passenger side valve cover, at the front. I, too, have a solenoid mounted on the side of the engine compartment, but I think that's the starter solenoid, or something similar.
What are your symptoms? Extended crank time, lot's of white smoke, but eventually starts? That's what mine was doing until I replaced the glow plug relay two weeks ago.
On my truck, the correct part was GP/109 from NAPA, but I'm not sure on your rig.
I hope this helps.

 

Quadzilla is correct, you are looking for the relay on the front of the right valve cover. I was thinking that you had the wrong relay thats why I asked. Also, to test your glow plugs... Take a test light and hook the alligator clip to the positive battery lead and remove the connectors from the glow plugs and touce the tip of the test light to the end of the plug. The ones that don't light are bad. For the system to operate correctly you need to have all plugs working. Good Luck.

 

I'm currently working on a 97 at the shop and its on the right valve cover as most/all.

 

appreciate the info

 

Hey psd tech,
Do you need the key on to check this??

 

The engine and key should be off. Remove the glow plug connector and touch the post that the connector slides on to. Basically your checking continuity to ground, I assume that most of you don't have a ohmmeter. Power from the relay and a good ground @ the glow plug and a plug that is not open = heated combustion chambers.

 

Thanks psd tech I will try that this weekend. If you would have said continuity check I would have gotten it. Glad I asked and you answered.

Thanks

 

No problem, glad to help

 

I would like to pick your brain for afew answers if possible about my 95 F350 5-speed 2-wheel drive truck.
I'm having a cold start problem and was thinking that it was the glow plugs. I went ahead and started to
take them out of the engine and checked them and the wiring circuit and checked out OK! That is when I
found that the relay wasn't working. The crappy book that I have which is a Chilton's said that the glow
plug system stays on from 2-10 seconds until the engine starts, and then cycles for up to 40-90 seconds
to clear the excess fuel. So I replaced the relay and and then the relay stayed on all the time, which
meant that the glow plugs were on all the time. So I unplugged the wire from the
relay and was trying to find out what times out these glow plugs!
I have been reading all these messages on this site, and it seems that the relay is the culprit.
But no one mentions about the timing of the glow plug system! I've worked on Mercedes for 20 years
and there are sensors that switch the glow plugs off after start-up. I see that some people put a
momentary switch on the dash, but I don't like rigging something without knowing that it is possible
to fix it right. Of course the repair books just suck when it comes to looking at illustrations. I you
have any idea of if there is something in the system that I can check or replace (timer,switch,relay,or
main computer) to get the system working right would be greatly appreciated.