Starts right up , but only runs for 3 seconds. . . crank-it for 45 sec. to start on 1991 Ford E-350

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My '91 ford E-350 Econoline Diesel 7.3 L
is starting hard. When engine is cold (not-
run-for-over-eight-hours) it starts up right away,

It can't be the glo-plugs, because it does start right up
on the first try. But after it stalls, I have to crank for about 45 to 50 seconds before it will start. Lots of blue smoke after it starts, but being a diesel, can't tell if that is normal.

_______ any guesses ?
_____ Shade-Tree-Mech.
(4) Answers
(4) Comments
I would run a compression test, because of the Blue Smoke, ti could be that your Motor is getting tired and won't stay fired after the glow plugs cool off. Also there may be oil leaking down from the valve guides and casing the smoke. A strong 7.3 should fire right away and stay lit. ( I used to be a Ford Tech )
Thanks, but why would it run just fine after it does start. . . . And it DOES ALWAYS START right up hot or on a cold engine. But of course as I said only runs about 3 seconds (on a cold start). And then just fine after the "long-crank" ? And always a quick start for the rest of the day if the time-factor is less that five or six hours. (?)
--- I think the blue smoke is because after cranking for 45 seconds, all that extra fuel is now in the exhaust manifold (?) And lets just say oil was leaking down to the cylinders (again) WHY WOULD IT START RIGHT UP (If for only 3 seconds) IT DOES FIRE EASILY.
It would seem to me if all that oil was sitting there, 'it' wouldn't want to "fire" ! (?)
{and I don't show lost of oil on the 'dip-stick' yet}

Here is the advice I have got so far, do you agree ?

And my book doesn't show the "CRANK & CAM" sensors ?
If you do agree that it could be the sensors (I don't agree) where are they
and can I get to them easily (?) (approx cost $) Don't want to be swapping out expensive parts just for the HE*L OF IT ? !
{to me this sounds like advice for a gas engine not my diesel ?}

=> "Swap out the crank and cam sensors"
___ "Faults with hall effect sensors are difficult to diagnose without an oscilloscope to capture the output. Timing is everything. The Engine/power control unit (ECU) takes signals from the crank sensor (CPS) to know where the piston is with respect to top dead centre. The cam sensor also tells the ECU when the piston is at TDC but it also tells the ECU whether the piston is on TDC for the power stroke or TDC for the fresh injection of fuel. If the ECU loses track of either the crank or cam sensors it has no real chance of maintaining the correct timing of fuel injection. Badly timed injection of fuel equates to an engine that is hard to start and prone to stall. If the timing is just slightly adrift the injection cycle might be short in which case the fuel mix will be lean. Lean burn is sustainable in a warm engine (you say yours starts easily when warm..) but makes it difficult for a cold engine to start and keep running (you said that it starts but dies quickly and is then difficult to get going....). From what you said I diagnosed that it was more than likely that the injection timing was off and since the cam and crank sensors are key to this but are a pain to confirm as being at fault but are also not too expensive or difficult to swap out that this would be a good place to start. If the problem persists at least you will know for sure that it is not the cam or crank sensors. Hope that helps give some back ground to my thoughts to what was, i admit, a very short solution. . ."
Dandd, what 'da-ya think ?
thanks again.~ shade-tree

Check the WCM (Wireless Control Module; for your key fob,) if you factor in the the 3 second run time. The WCM has effectively tricked you into continuing to attempt to start it while waiting for the police to arrive. $430.00 was price for part, install and programing of the part with a very expensive scanner.
Dodgie-guy, Now say it in English! (?) . . .Without all the "police-arrive-crap" !
. . . how does this sound for a good guess?
=> On the fuel filter head there is a return line (5/16", I think). The barbed fitting the hose attaches to is actually a check valve. The rubber inside the check valve deteriorates (over time) and the valve no longer works and a bubble of air forms at the filter head...very common problem which few seem to know about. It takes a few seconds for this bubble to make its way to the injection pump. The Ford part # is
(or was) E9TZ-9K061-A.
(? got one on your Police Dodge-diesel?)
Dodge3500 The result in my case was the WCM. Different WCM manufacturing and programing result in different system faults and failures to deter theft. I'm thankful for the return-line tip and will be looking out for it. Would it not bleed off in the fuel tank, as it is a return? As for "the cold start is great," in theory oil leaking by worn parts may increase the compression and promote ignition in a worn engine. As for faulty electronics, there is always a chance short or disconnect. I agree with the issues related to trouble-shooting electronics as temp and humidity can alter results drastically and people have purchased defective, "NEW Parts." The temp and humidity issues were first discovered in coils of gas burners.
Like Dand D said the engine stays running while the glow plugs are hot once they cool because they are shut off when started, the compression is probbably not high enough to keep the engine firing. You need to pull the glow plugs which are fine and do a commpression check on each cylinder.
. . .Then WHY DOES IT RUN (and start just fine) for the rest of the day?
(If the glow plugs were bad, it wouldn't start just fine hours later that day!)
Keep in mind IT always starts and runs 'smooth' for the rest of the day.
=> Even 5 hours later after sitting, starts right up !

NOTE: See my guess below under "Dodge3500"
-------"fuel filter check valve"
Dodge 3500 I was informed of another Ford wrecker with similar conditions, turned out to be injector seals. Ordinary O-rings will only have you pulling them to replace them with OEM seals.