7.3 slow crank/no start

[rohleder644]

I searched and couldn't find anything that was quite what i'm experiencing. I've got a 99 7.3 that isn't wanting to start. Everything has seemed very normal, no slow start whatsoever. Jumped in the truck after having made a couple trips already that day, and it won't fire. Wts light comes on then off, turn the key and it cranks over slower than usual, but not significantly slower. The dome light dims and even turns off sometimes. I get crazy flashing dummy lights and a rapid "clicking", almost a buzzing that sounds like its coming frrom the dash. Voltmeter looks like its showing a little low, but still in acceptable territory. I thought maybe i had 1 dead battery so i put a trickle charger on for a couple hours and still the same thing. Pulled both of them and tested them, they check out fine. That's the extent of my guesses.......any thoughts?

[wstrnhauler4x4]

make sure your tach is bouncing while cranking. check fuel pressure at the schrader valve if the tach moves.

[Toms01PSD]

No idea what it could be, but I'm curious why people say the tach should bounce... I've had my truck for 1 1/2 years and I've never seen my tach bounce while cranking.


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[HVAC SuperTech]

Tach only bounces in the obs trucks. Not ours.

To the OP...
Could be your starter is bad. ..I have heard solenoids going bad on them causing slow starts. And if the truck isnt turning fast enough then it won't start. Try hooking jumper cables from another vehicle to it.... can take a meter and see if there's a huge drop in the voltage when you crank on it. A sign of a bad battery.... sometimes the tester can't find that

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[NoRalPh]

The Tach actually shows cranking rpm up until a mid-year change to the electrical system in 2001 (if you have an '01 with a Trans Temp Gauge in the cluster, you got this upgrade and the Tach is no longer driven by the CPS)

To the OP, in a 99, the cranking rpm and voltage to the PCM is critical. Not fast enough, or high enough, and it's Never gonna start (did jumping it make it crank significantly faster?) In the cold, Everything's Got to be right with the Batteries-Starter-Cables or you'll have trouble...

7.3hard start cold no codes - YouTube

7.3hard start cold no codes - YouTube

Cranking Fast Enough?

[HVAC SuperTech]

my tach doesnt move. i dunno....

but yes, noralph is right...you have to have it spinning fast enough to start it, otherwise combustion temps wont rise in the cylinders and the fuel wont be ignited to produce the power stroke.....funny how that's what its called and thats what our engines are....lol

[Mission7.3]

Check your starter solenoids

[Toms01PSD]

Originally Posted by NoRalPh

The Tach actually shows cranking rpm up until a mid-year change to the electrical system in 2001 (if you have an '01 with a Trans Temp Gauge in the cluster, you got this upgrade and the Tach is no longer driven by the CPS)

To the OP, in a 99, the cranking rpm and voltage to the PCM is critical. Not fast enough, or high enough, and it's Never gonna start (did jumping it make it crank significantly faster?) In the cold, Everything's Got to be right with the Batteries-Starter-Cables or you'll have trouble...

7.3hard start cold no codes - YouTube Cranking Fast Enough?

I don't have a trans temp gauge in my dash but my tach doesn't jump while cranking either... Doesn't make much sense to me.


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[NoRalPh]

You don't see the needle move up at all when cranking it over on the starter? It should...

Before the upgrade, where the GEM Module was replaced by the VSM and many of it's functions were "spread-around" (one of them being the Cluster), the CPS kinda drove the Tach needle more directly. It became it good indicator that the CPS, which had a high failure rate, was functioning. If you didn't see any Tach movement while cranking, it was probably bad (yours isn't of course if the engine runs ).

Look carefully, maybe "Bounce" is more than you're actually looking for. It should rise slightly, indicating like 150rpm, where the upgraded '01's and 2's & 3's show No Movement what so ever. If yours doesn't also, I don't know why...

[Toms01PSD]

Originally Posted by NoRalPh

You don't see the needle move up at all when cranking it over on the starter? It should...

Before the upgrade, where the GEM Module was replaced by the VSM and many of it's functions were "spread-around" (one of them being the Cluster), the CPS kinda drove the Tach needle more directly. It became it good indicator that the CPS, which had a high failure rate, was functioning. If you didn't see any Tach movement while cranking, it was probably bad (yours isn't of course if the engine runs ).

Look carefully, maybe "Bounce" is more than you're actually looking for. It should rise slightly, indicating like 150rpm, where the upgraded '01's and 2's & 3's show No Movement what so ever. If yours doesn't also, I don't know why...

Ill take a video of it next time I drive it so you can see. Doesn't move at all!


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