Greguw

Hi Guys

I just finshed putting on as many parts that I could ...I need to order a bearing block , fan clutch , upper and lower rad hoses , and may be two new batterys .

My question is , I did not have the belt on and I was moving the truck around the shop ... The voltage was around 12 ... no belt so it was not charging .

I pulled the truck out side to clean up and it would not start ...it was cranking fine ... but no starting , I only had one of the batterys hooked up , I checked that front crank sensor ..it was fine and I tighted the battery terminals again ...it fired up .

My question is how dose 12 valves run, do they have a computer? ... whats the crank sensor on the front for ...? do they have electric fuel pumps and I always here talk about lift pumps , what are they ...?

Basiclly in a nut shell how do they run ...?

Thanks Guys

Greg

JKM

Basically , the starting operation goes something like this:

on your injection pump , there is a shutoff solonoid , with 2 functions , lift , and hold, When you turn your key to on, nothing happens in the starting circuit besides the cycling of the grid heaters, when you turn the key to start , the LIFT fuction of the solonoid is carried out , allowing fuel to flow and the engine to start. When you release the key to the on position, the lift function stops , and the hold fuction takes over , holding the solonoid up and continuously allowing fuel to flow. There is a blue fuseible link coming off of the driver side battery that is tied in with this whole circuit, it sounds to me like maybe you had a bad connection on that blue wire, which did not allow the solonoid to lift and turn the fuel "on" allowing the truck to start.

You truck does have a lift pump , but it is mechanical , and they very very rarely fail. Your injection pump is a bosch P 7100 mechanical injection pump , used from 1994-1998.

1998.5-2002.5 saw the use of a VP44 computer controlled electronic injection pump , and it had an electronic lift pump also, those are the ones you hear about failures on.

The crank sensor on the front is basically just to tell the computer that the engine is running, the computer then allows the a/c to run , and the alt to charge , etc.

Greguw

I did find a wire that is blue , but they put a fuse holder ...I will have to trace the wire ... thats the little stuff you get when you buy used off a lot.

The truck need a lot basic mantance things , but I am pretty happy with my purchase so far .

Thanks

Greg

John Faughn

I had a problum like your , it was off & on after check many times , it seemed like every time I got set up with test eqquipment it would work , so after looking at a wiring diagram that was sent to me by some one on this site I took out the pull relay and pulled the cover off and looked at the points and saw that one was burnt , I filed it put back together and it was fixed . just a possiblity for a cheap fix.

Greguw

Hi Guys

Are these a standard small block relay and where are they located ...it would be good to give them look .

Thanks

Greg

infidel

John Faughn

I found mine on the top of the fire wall just off center on the drivers side hanging off the lip where the back of the hood seals , there are 2 of them there the easy way to tell was to look at the flat conectors are much large for 70 amps , they do look like the reg. small box relays , and can be tricky to get the cover off with out braking the plastic , if you do just use some silly cone to seal it back up. then to file the points remove the spring and the holder for the top have of the points should pivot out to make it easyer to file . thats if you see that the points have a black burnt look, if not look els were for your problum.

Greguw

Dose that fuel shut off relay control both lift and hold , and I did read some thing about lift pump failure ... some guys run fuel pressure gauges ...?

Thanks guys

Greg

JKM

The guys running fuel pressure gages have 24 valve engines with the electronic pumps , they monitor fuel pressure in order to monitor the lift pump condition , your truck has a mechanical lift pump , failure on them is very very rare.

infidel

Just the lift circuit goes though the relay.
Here's a schematic, look at top right side https://www.dieseltruckresource.com/...sort=1&cat=500

I use a fp gauge on both of my 12 valves. It's a inexpensive gauge that can keep you off the side of the road and pays for itself rapidly by allowing you to skip unnecessary fuel filter changes.

grow_ctd

A heavy duty replacement relay is available from larry B and I recomend his heavy duty replacement starter contacts if youve got many miles on the starter real easy replacement project and could save you a lot of money, I just had my contacts stick and they burnt Up my solenoid Dodge wants 5 Bills for the solenoid Larry B's 200 but the contacts are much cheaper to prevent damage. Check (Fostertruck.com)

John Faughn

Hay back again, the solinoids do not control the the relays , its the other way around the relays control the solinoid , this is becouse there is a heavy currant to pull the linkage up , and that reminds me of an other way to test and get you going , when the truck turns over but does not fire , and it is this problum , then to check this out reach for the linkage at the bottom of the solinoid and lift straight up , with the ingition in the on position , it should stay up until you turn off the ing. . Now with the linkage in the the up position , with out turnning the ing. off , turn turn the ing. sw. to the start pos. [ and if the relay is your problum then the truck should start and run] if not and you did every thing els right then your problum is some were els.