Recently purchased a 1998 12 valve with only a 150000miles appeared in excellent condition no rust and very clean low miles . However after only driving it a couple of hundred miles it started to stall out going down the road or when I slowed down to make a turn . No shudder just shut down and coast to a stop . Would start up again after 2 or 3 tries 20 second cranks hold the pedal down . The last time it kept stopping again after every 1 mile or so .. Gave up had it towed . It would even stall when the fuel solenoid was wired up !

Ive replaced the fuel pump and fuel solenoid also fuel relay ,fuel filter ,,, Fuel heater was by passed live in the south
. ., checked line for leaks ,Did this right away as I needed to do the killer doll pin anyway .[[ it was out by the way chipped a tooth on the pump gear]] ,,
Had the brain box replaced,, had too because the cruise control relay was in it and cruise wouldn't work ..MY mechanic that programmed the brain suggested to go ahead and replace the wire harness too,, so I did,,,as shaking it seemed to let it start,, looked funky anyway got a rebuild .. Crank case sensor came up bad on a computer ok done and replaced .

Last time now on a brief drive it started to shutter a bit but didnt stop however I came back right away don`t want another tow bill .. AS [I]`m new to this truck and told there bullet proof what the h__ is going on,, any and all suggestions would be Greatly appreciated .. !

 

Idle adjusting screw is at rear of the pump on the bottom. 10MM wrench needed to loosen lock nut first then you can turn adjusting screw. Turn it clockwise about 1 turn and then tighten lock nut, make sure adjuster doesn't turn with it. Idle speed should be set at operating temps. with trans in gear with a/c on. Should be 750 RPM.

 

What fuel pressure is it running after the lift pump?
If you don't have a fuel pressure gauge I would suggest getting one to help diagnose the problem.
The filter "sock" in the fuel tank might be very clogged.
It could also be sucking air into the fuel line somewhere.
Fuel lines from the tank to the lift pump will not show a fuel leak as they are under suction and will just suck air in and be clean and dry looking.

 

Also check vents in fuel tank make sure they are not plugged. If the bottom of tank is sucked in they are plugged. Agree with Oliver put a fuel gauge on it.

 

Check all the battery cable connections and cables. Sometime cables erode inside the sleeve. If you have a loose connection the fuel shut off solenoid will kick out intermittently. Mine was doing this but it burned up before I found the loose connection.

 

Marder,
He mentioned it would stall even with the FSS wired up.

 

Oh didn't see that.....hmm

 

Yeah if those 12Vs have fuel and you get them turned over, they usually run till you're out of fuel or close the FSS.
I am leaning to a fuel delivery problem.

 

hmmm ok yes it does shut down even with selinoid wired up . battery cables appear to be fine , truck does not have a fuel pressure gauge on it but I will get one and put it on . thought about this pulled the line off once after the pump was put in seemed to have great preasure . I was leaning toward electrical problem it is my understanding that if any sensor get or give a false reading that is sent to the brain box and the engine is shut down .

when the truck stops it's not like it runs out of fuel there is no stop go or shudder it's just like if the key was turned off dead and coast to a stop ..

it will be next week before I get a chance to hook up the preasure gauge . live in the sticks will go to town on Monday or order from Genos .
any other And All IDEAS appreciated

Haven't had this truck long was super clean bottom was preasure washed and hide the fact rear wheel seals were leaking and also the pinion seal . so I found that out after the purchase IThink this also is an on going thing and why it was sold with only a150000 miles on it . I was looking for this 12 v for 2 years before I found this one .. I have 3 old Isuzus diesels great trucks needed a larger one .. Thanks for info guys

 

I can get my 12Vs to fire up sitting on the shop floor with the FSS wired up or hot wired, with just a jerry can of diesel and a battery to turn it over.
No "brain box", no sensors of ANY kind needed for a 12V to run, as they are completely mechanical.
Unless the three month only run of '98 12Vs has something I am not picturing off the top of my head going on.
They run on air, fuel and compression ignition.
You don't have a banana in your tailpipe do you?

 

Brain isn't that smart, only thing that will de-energize the fss is the key or a failure of the circuit.

If the fss is tied all the way up and the linkage to it is correct, it will run until out of fuel regardless. Need to verify fuel pressure to the pump.

Does the pedal go really stiff when it dies? Does it shut off while accelerating or as its coming to idle/foot off the throttle? Always a chance of an internal governor problem in the injector pump.

 

fuel pedal is normal when it dies , no telling when it will shut down happened twice when I slowed for a turn once at idle when I was parking . 5 times in the same day going down the road at speeds from 55 to 20 mph .. 1 other time at about 65 . fss was tied all the way up and it was a new one ,,checked it before I tied it ,,it was working . Never shut down upon acceleration .

nope checked tail pipe for the banana none there , however wife thinks there could be a Spirit living under the hood ..

 

Where is the best place in line to place the fuel preasure sending unit . ?
also any recommendations on whether mechanical or electric unit . Hope to get her done early this week then go from there ..

 

The PM you just sent me with the same question was answered in a return PM.

 

Any progress?