2001 7.3 slow crank/hard start

Marc · January 21, 2006

Got a f250 crew cab in the shop with a slow crank. The owner said that when it's above freezing the truck started fine but under 32F he has to jump start it and then it runs rough until it's hot. I got cylinder balance codes for #1 and #7 cylinders. I replaced those injectors and the miss fire/rough idle was gone. I had good ICP pressure (550psi at idle and built up 2300psi cranking really fast) But the slow crank is the thing that killed me.

The stroy goes like this. Customer bought the truck last summer and it's from florida but now it's here in Sweden. He has never had to start this truck in the cold until now. I have only 115rpm and that only lastes for about 10 seconds then it's dead. I have tested the batteries and they were bad so I put new ones in(ac delco's 850 cca at 0F). Same problem, max cranking speed 115rpm this time for 30 seconds so before I started losing speed then I put a starter in it, thinking that it's drawing too much amps out of the batteries,(we don't have a amp meter at the shop so I couldn't see how many amps the starter was drawing and the customer had a new one with him) Same problem. /forums/images/%%GRAEMLIN_URL%%/banghead.gif

So now thinking that the cables were bad (the termanals were corroded and would never get fully tightend to the poles) replaced those, SAME THING!!!!! Slow crank! /forums/images/%%GRAEMLIN_URL%%/mad.gif

I feel like a total shot gunner here. I can't understand why its still has a slow crank. Specs are about 150-250 rpm cranking speed. He is using 15W/40 (condition is ok) but that should work at these temps. I see that someone has been in the motor(different/missing bolts everywhere and the lift hook was bent). I was thinking of some type of base engine problem. This has a superchip software and a K&N filter charger on it. When I drive the truck, it doesn't sound right to me. Abnomally loud and you can here the turbo spooling like crazy. This thing is a POS but I still need help figuring out what went wrong here. Thanks /forums/images/%%GRAEMLIN_URL%%/cheers.gif

HGM · January 21, 2006

Are your batteries going dead after 30sec crank time(?They are good, not just new, right??) or is the engine locking up? I would do a voltage drop test on each part of the starting circuit and repair excessive resistance.

If that doesnt show anything a compression test may help give you an idea whats going on. With the K&N, I would expect low compression but its spinning slow, not fast.....?.. Are you loosing coolant? Any smoke?

BTW, I would remove the chip.. Dont know that it would effect the starting, but you never know..

Keith Browning · January 22, 2006

The ONLY three things I have seen that caused a slow crank condition were bad batteries/dirty terminals, loose engine ground and seized front end accessories (a/c compressor, water pump, idler pulley) You have covered the basics so perhaps you need to look at the more unlikely items. Coolant freezing up putting drag on the FEAD belt? Don't laugh! We ran into about 5 6.0L's that would not start due to seized a/c compressors. The engines would not crank above the required 100 RPM on most of them. The others cranked slow but fast enough to start and they made "high pitched noises" while running.

Marc · January 22, 2006

I am going over to the customers house on monday morning to take the truck to the shop.

The chip software will get removed on monday for sure /forums/images/%%GRAEMLIN_URL%%/smile.gif I will try to just remove the drive belt and crank it over. That's a good idea. I will monitor the coolant level (I did install 2 block heaters in it and the freeze point was -36C) and the batteries are brand spanking new but I will test them on monday.

I still think about a base engine problem but less compression would make it crank faster so /forums/images/%%GRAEMLIN_URL%%/confused.gif but it runs good when you drive it (after I replaced 2 injectors). I still think that it's a little noisier than normal though /forums/images/%%GRAEMLIN_URL%%/frown.gif

Marc · January 23, 2006

Ok, tried to remove the superchips software, it wouldn't let me(could be cause I reflashed it before when I had a p0605 code). It programmer says to call superchips error code 9. I have noticed I keep getting a p0603 code in memory.

I have removed the drive belt, still slow crank.

I have tested the batteries, no bad cells, they are good both with 850amp cranking power. Each one goes down to about 10.9-11.5v while cranking(only 115 rpm still). I have removed the filter charger and still slow crank speed. I noticed that the fins on the inlet side of the turbo are rounding off /forums/images/%%GRAEMLIN_URL%%/frown.gif . The turbo is not in good shape but still that wouldn't choke the air some much that it would have a slow crank.

I know that he had a trans overhaul last year before winter. Could there be something there? I guess there is not enough clearance to just remove the converter nuts, push the converter back then crank it over or take the HP oil pump out and crank it over.....I don't know /forums/images/%%GRAEMLIN_URL%%/confused.gif Everything that I am looking at now seems to be a stretch. What base engine problem could cause this load while cranking?

HGM · January 23, 2006

The turbo is because of the great filter he has in it, like you said its secondary.It's probably going to need an engine due to the dusting but you need to make sure there isnt something else there.. I would try another PCM,if you have one, before getting into removing the trans. You could also bar the engine ofer and see if you feel excessive drag. Its not scientific, but might give you an idea..

Marc · January 23, 2006

I was thinking that I have to get a ratchet and turn the motor over to see what it feels like. I would like to try another pcm but I cant get my hands on one with out having it sit on the shelf if it doesn't fix it. We'll see what tomorrow brings.....

Keith Browning · January 25, 2006

Quote:

What base engine problem could cause this load while cranking?

Two of the many 2003 6.0L engines I have replaced had melted piston crowns due to a faulty injector. They were both municipal vehicles so they most likely would never have had a tuner on them. We were seeing quite a few injector problems back then. I do remember one of those would not crank fast enough to start. Just an idea.

HGM · January 25, 2006

Quote:

What base engine problem could cause this load while cranking?

Two of the many 2003 6.0L engines I have replaced had melted piston crowns due to a faulty injector. They were both municipal vehicles so they most likely would never have had a tuner on them. We were seeing quite a few injector problems back then. I do remember one of those would not crank fast enough to start. Just an idea.

Yes, good point. The more fuel delivered by the chip could cause this.

On the 6.0L we have seen sticking turbo's causing overboost and melting pistons, seems like #3 is the most common. Make sure you check boost pressure and turbo operation when you have a 6.0L piston meltdown.

Marc · January 26, 2006

I checked the turbo fins and they look BAD /forums/images/%%GRAEMLIN_URL%%/eek.gif

Rounded off and it looks like the fins starting to bend out.

I tried to remove the superchips software but it gave a truck mismatch. I think it was because I reflashed the pcm but I am not sure.

I truly think that this is a base engine problem. The customer is havinig a hard time understanding this. He still thinks that it should run bad also if it was a base engine problem and this is some kind of ground problem. :rolleyes:

We'll try another starter and I will do a relative compression test with my laptop using IDS for the 1st time /forums/images/%%GRAEMLIN_URL%%/laugh.gif I think I might find something there.

HGM · January 26, 2006

I wouldnt waste my time on a relative test... It is just that, if 4cyl are bad, they all show good.... In this case since it has been dragging on for you, I would do a manual test to find out the truth. Just my opinion of course..

Marc · January 26, 2006

I was thinking that too that the test is "relative" but it's a quick way just to see if there is a difference in any of the cylinders, if all of them are bad then I get nothing out of it. I need to get the adaptor so I can do a real compression test.