2001 Ford F-250 7.3L diesel 4x4...Ok, Here is where I am. Sometimes truck will not start, I am getting feedback (buzzing) back through a relay under the dash. It opens and closes (buzzes) while I'm cranking the engine. May not be conected to the problem I don't know. If you go through the whole "wait to start" process it will not start. But if you are cranking the engine over and just turn the key off and right back on real quick and crank it over it will start. Its kinda like you are skipping the whole "wait to start" process. It will start every time if you do this, and the relay under the dash doesn't buzz if you just turn her over and crank her up. The relay I am talking about is under the dash below and to the left of the CD player, there is three of them, one blue, normal size realy, and two small black relays, about half the size of the blue one. I also noticed that when you turn the key to the on position the vacum pump located on the passenger side runs constantly. My A/C went to the defrost only one trime however and I haven't checked the 4WD yet. I don't think the pump is still running all the time right at this moment but I know it does more than not. So in short I have found by playing with the starting process I can wait fior the "wait to start light" to turn off, crank it over and hear the relay buzz, let off the key to stop cranking and and quickly start cranking again and it will start, and the relay doesn't buzz while cranking if it starts.....? Please help me befoe I jump from the roof of my house !!!! Thank you in advance guys. Mike Saylor.

 

Oh, and one more thing.... On the A/C, upon starting the truck if you are in 4WD it takes around one minute for the A/C to switch from defrost to vent, if you are in 2WD it takes about 5 to 8 seconds to switch from defrost to vent. If the truck is running and the A/C is blowing through the vents and you switch the selector to 4WD it will stay on the vent for about 30 seconds and then got to defrost, turn the selector to 2WD and about one minute later it switches back to the vents...Leaky line or bad pump...? As far as starting, it still starts and runs fine as long as you trick it, just gotta crank it over turn it off and hit it again real quick before....well, just before.. I guess when we figure out what before is we will know the answer to the million dollar question. Thanks again, Mike.

 

take it one at a time. test your v-pump- should be pulling at 20psi. if it is, then you have a leak.

I would then get another gpr and put in. I did that just to have an extra one. ($34 brand new).

 

what does your volt gauge read while cranking the engine, sounds like you may have weak batteries. mine did that relay clicking/buzzing thing when the batteries where going

 

I'll check it with a volt meter and tell you in a few minutes... Meanwhile let me ask you this, If its the battery then why will it start just fine when I start it quickly after the "waiting to start" light goes off...? After I crank and crank it I just simply let off the key and go right back to cranking it and it starts.... Here is one to scratch your head about, I got it started and pulled the relay that was buzzing (the small one under the dash below the CD player) and it startred running poorly like they do when water is in the fuel, wouldn't build boost or anything, then I plugged the relay back in and it started running fine again. now remember, I done all this while the truck was running, after this, the truck would start up just like normal for a few times then go right back to how it was doing... I'm thinking if someone can tell me what those three relays go to then I will find my problem. I have called every ford dealer I can think of and know one can tell me... One relay is blue and normal size, the other two are side by side and the are the smaller relays (about half the size of the blue one) and they are black in color. I have replaced all three, not the problem..... Anyone know what these relays power....? Thanks guys.

 

What is a GPR...? What line should I pull from the pump to test the vacum..?

 

GPR=Glow Plug Relay. It is under the hood. Test the main line coming from the v-pump.

 

The voltage is 12.50 with the key off, 13.00 with the truck is running at idle and 13.40 - 13.50 at high RPM's and around 9.98 - 10.00 while cranking.....You know it cranks plenty fast enough it seems, it doesn't sound as if it is draging, however I would think it should charge around 14.50 myself... About a week ago I turned the key to the on position and all the dash lights gauges etc blinked off and on real fast for as long as the key was on, I went to start it and it just went "clunk" and it seemed if all the power failed then I turned the key back and forth a few times and it quit doing that and started just fine..., I almost forgot about that...You said if it pulls 20PSI then I have a leak, and if it doesn't then the pump is bad correct...? Where exactly under the hood is the GPR..? Does it pertain to the un-explainable starting after the wait light as I described...? And again, does anyone know what the relays power that I asked about..? Thanks fellas.

 

My guess would be weak battery/ies. You can get them load tested to check. Remember, these engines require batteries to be at peak perfomance. Anything less will present the problems you list. Both batteries need to be in good shape. Other things to check would be you connection. Loose or corrosion will cause problems as well.

 

are you sure the buzzing is actually under the hood? when you have weak batteries, the voltage will be teetering on the edge of "good" and "no im not starting". the contact ring in the starter solenoid will move the plunger in and out rapidly as the voltage spikes, and you get the clicking noise. if you stop it all of the sudden and let the voltage spike upwards again, then the electromagnet pulls the contact ring inward to complete the circuit once again, and then the engine cranks over and may start very quickly.

 

Yeah, the noise is under the dash. I can actually grab the relay (I have the dash panels off) and feel it opening and closing rapidly (buzzing). The truck cranks fine, I know the noise you are talking about, like when you have a bad ground or something, and the solenoid just clicks and don't actually even turn the motor over, my truck is cranking and the relay is dropping. Soooo, I dunno. but my problem is different as my truck cranks away. I cleaned the post and terminals, the batteries look old. I have had it for 3 years and I have never changed them. They are older than that I know. Under load (cranking it) the volt meter falls down to the 9.50 - 10.00 range...and sometimes 8.90. I don't think that is enough under load, well not for the 7.3 anyhow. What do you guys think..?

 

no, that means the batteries are getting to the end of their life. the PCM requires about 10.6 volts to function properly.

 

dead batteries,
strokin is right, use to do tires and batteries in college as my part time job. you don't want to ever see anything below mid 10's in the voltage range. causes all sorts of problems. and your alternator should be charging anywhere from 13.5-14.5 (generic number for most vehicles). at idle you may only see the 13.5. hook up multimeter leads and set the meter so it can be seen in the truck, rev to 2k and see if the voltage is accetable. around 2-3k is where most vehicles are designed to cruise, 2k is more appropriate in our trucks, so this is where everything is working the easiest. this is more accurate with fresh batteries though. don't want a low battery draggin down all the voltages.

 

You had better get some new batteries. Those are at their end and the longer they are in the more they take their toll on your alternator.

 

Ok, OK, Ok, I'll buy new batteries..lol.. Thanks a lot guys. I didn't know the PCM needed 10.0 + to operate properly. Now I do !! Thanks a lot. I will post and let you know what happens. Thanks again. Mike