Ford Powerstroke Diesel Forum banner

Post PCM no start and hand prime

5K views 44 replies 10 participants last post by  JamieSinns 
#1 ·
i'm 2nd owner of this truck. been reading a lot of posts before starting this thread. here's the deal:
PCM smoked and found an aftermarket chip assembly installed in it. replaced PCM. i'm going factory this time. NO CHIP!
the truck cranks and cranks. i can hand prime the truck and she runs great. my fuel pump does work, my filters are ok, it's just she won't get fuel with the key. what's up with that? i'm tracing wires and trying to figure out where the failure is in this logic. am i missing something? any words of advice?

99 F250 7.3L auto 2wd.
 
#2 ·
When you say "prime" you're putting fuel in where?

Here's the Quick & Dirty NoStart list;

WTS Light? - do you get it when you first roll-on the key? (shows the computer is running)

Do you see cranking rpm on the Tach? Do you have a spare CPS to try?

Is there fuel in the fuel bowl now? Does it refill after cranking? (open the drain level to check)

Can you hear/feel the pump running (below the dr seat, against the framerail)

Could the fuel gauge be giving a bad reading? (Below 1/4 tank?)
 
#3 ·
i'm trying to help my mechanic out.
no on the spare sensor
he said he hand primed the truck and it fired up and ran. fuel pump runs good.
wts light good
i'll ask on RPMs on tach while cranking
best i can remember truck is low on fuel in tank. but when hand prime is complete, truck runs.
just won't do it under key by itself.
 
#5 ·
The Low-On-Fuel is what would concern me...

You could have a problem, in the tank, where the pick-up and mixers crack allowing air to be sucked instead of fuel (not an UnCommon failure in our trucks).

Here's a link to a mod to eliminate the problem -> Welcome to guzzle's In-tank Hutch Mod Web Page

OR, you could simply have a bad Sending Unit (in tank) telling you there's more fuel in there than there is and you're simply OUT ;)

Either way, next is to verify fuel from the tank is getting to the pump.
 
#6 ·
thank you! i'll work on that step next! thanks so much for the online help. can you tell me one more thing? why is it that today's diesels have so much computer crap on them? i remember back in the day that the kenworths,peterbilts, caterpillars and what not didn't have all of the sensors on them and they ran good? let me guess, the govt got involved? :dunno:
 
#7 ·
Emissions is one reason, another is technology advances.

just like why do gas motors now have computers and injectors? yes the metered fuel leak of the carburetor's worked, but injection is so much better for emissions, fuel milage, and drivability.
 
#8 ·
ok, here's the latest on my beloved truck:
i hauled some diesel out to it and put it in. fuel gauge came up to 1/4.
turn key on, get WTS light, i hear the fuel pump kick on, it cranks, no smoke and no fire up.
only code that's popping up is backpressure. that should go away once she fires up and runs shouldn't it? we're pouring through the wiring harness to see if any wires are bad since my old PCM smoked. it did smell like smoke.
still working on the truck, we'll find the problem unless someone else knows the answer, but we'll eventually get it going and then we will post the solution. but in the meatime, if you got some ideas, please pass them along.
 
#12 ·
what tells the fuel pump to kick on?

when i turn the key to "on", the WTS light comes on and then goes off, i presume to where the glowplugs have done their thing, then during this process, what tells the fuel pump to kick on when you turn the key on? i'm wondering now if that is my problem? :dunno: i thought i could hear it turn on. now i'm unsure.
 
#14 ·
If the engine is deemed "cold" (by the EOT sensor) the GPR is activated (this has Nothing to do with the WTS light). Next, the fuel pump is powered for @ 15sec. (times-off if the engine isn't running). You should be able to easily confirm it's at least running by putting your hand on it (below the drivers seat on the frame rail).

Once the PCM sees at least 100rpm (on a '99 you should see the tach needle rise up on the starter to confirm), the system voltage is above 10V (lower on newer PCMs), and the HPOP pressure rises to over 450psi (by the ICP) the PCM triggers the IDM to fire the injectors.

If the injectors spray the right amount good fuel, there's sufficient compression, the flow of air through the engine is what it should be, the GP's are working (if cold enough to require them), it should Start :wink[3]:
 
#17 ·
Sinns, you need to do the HUTCH mod. Before doing that, get urself another 5gal d2 and some 3/8 30r7 fuel line. Pop the "suction" side oem line off the fuel pump, and rig the 3/8 30r7 line to it and into the 5gal can. Now, turn key to "on", let WTS do its thing, then wait additional 1min. Now try firing her off. if so, drop the tank and to the mod.

Even with mod done, dont let it get to 1/4tank, its just not good on system, since its that low, swashing around, ur pulling air into the fuel system.
 
#21 ·
My f350 ran rough for a couple of seconds then died. It would only crank over with no star. It only showed a cam sensor code. I replaced it with 4 different ones and still no start. Next I replaced the ICP sensor, still no start. Finally replaced the Ipr sensor witch is on the HPOP (high pressure oil pump). After three tries I pumped the gas and she started up. It took a minute or so and she idealed out smoth.

Try replacing the IPR sensor. $200 of amazon.
 
#22 ·
The IPR is a valve, not a sensor, and it does sit on the back of the HPOP (high pressure oil pump). This pump sits under the fuel filter housing. The IPR valve regulates the pressure of the oil in the injector system. I would not go throwing $200 into this valve if you do not know that it is the problem. How much pressure is the HPOP making when your cranking? It is almost impossible to diagnose these engines without a scan tool of some kind. Did this truck ever run for you? Did you buy it not running? It would be nice to know what lead up to this happening.
 
#23 ·
With all the computers and sensors which allow you to have a truck with so much power, you need a computer program to monitor possible problems with sensors or use the sensors to watch systems to see what is not working right.
 
#24 ·
A broken ring is not going to cause the truck not to run. It would run, but not well. It would miss and buck, but it would run. The 7.3 Power Stroke will run on four cylinders, not well but it will run. The problem is somewhere else.
 
#25 ·
well if you're talking about my truck, i am the 2nd owner. previous owner chipped it. it didn't know this till the PCM smoked. i bought truck at 92000 miles, now have 130000. no issues till the other day. coming home and idling for a turn to my house. RPMs dropped by 200! no throttle, it shuddered when i pressed the foot pedal on this automatic. low idled home. changed fuel filter. no start. trailered it to mechanic, hard code-Bad PCM. replaced it. had it flashed, have fuel going to filter, tach works, 1/4 tank of fuel, he said he can hand prime it and she'll fire up and run, but won't fire up on its own when just turning on key and letting everything do itself. does that make sense? did i explain it good enough? we're getting no codes except low backpressure. i'm trying to learn as fast as i can. i read multiple posts everyday hoping to find a solution to try on my truck. cam sensor replaced a few months ago on recall. mechanic does have a computer/code reader. i think i'm going to buy one myself just to have around.
 
#26 ·
Ok, I am sorry for asking this if it has been covered already, but what does hand primed mean? How and what is he hand priming?

Just to help you and others the best way to mechanically check for fuel pressure to the injectors is to pull the 1/8" pipe plug in the fuel rail on the passenger cylinder head. You can adapt a mechanical gauge into this 1/8" port. This plug sits near the front of the head and I believe that an 8MM wrench is needed to remove the plug. If you have pressue at this port then you have pressure to the injectors. WARNING: When you install the plug back into the port after you are finished, do not over tighten it. If you overtighten it, it can and will crack the cylinder head. If this happens the head is garbage.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top