Ford 7.3 PowerStroke

[DestinBound]

Hi folks, the new project is a early '99 Ford 7.3 PowerStroke with an oddball problem. Figured we'd check with the Motor heads here - never know who has run across what!

The issue is with the start circuit. 9 times out 10 it will start just fine but that 1 odd time the starter will grind against the flex-plate and not engage. Try again and its fine. The previous owner rebuilt the stater and replaced the flex-plate with no change in symptoms. Apparently it has been doing this since new.

The start system is rather complicated and it is routed through a number of safety checks before the starter is triggered; neutral/park, etc., and all that is tied into a solenoid on the fender that has two legs. One leg for battery power to the starter motor and one leg for the starter trigger. Nothing seems to be wrong in any of this, but something is.

We're wondering if anyone here has run into anything similar.

[UrbanSportDog]

I have this truck and I've had and solved this problem.

Mine is an early 97 which is basically a '96.

First: Replace the starter. Watch a YouTube on it as there is a trick to the final bolt that is a huge PIA if you don't know to use the extension on your ratchet.

2nd. Replace your battery terminals with the marine style terminal and cable lugs. It's basically a series of 1/0 2/0 and 4/0 cables. Clean the copper good and get a good crimp. I used a hammer crimper and crimped everything in place. For most of the batteries there is enough cable to get the cable and hammer crimp to the steel at the the front of the body. For the main positive line I put a piece of 3/4 plywood down over my battery and just hammered it in place.

Use a dialectic grease and some quality heat shrink to finish out the battery project and you should be good.

That engine, especially on startup, sucks a huge amount of power and it has some components in it that protect it from bad electric. With the vehicle being as old as they are you almost always have a bad connection around the terminals. By resolving that and upgrading your starter motor you should be good to go.

Also, just an FYI, your starter will probably pass a bench test. That does not mean it's still good. Without any load the starter motor engages just fine, however, you ask it to crank that big heavy engine, especially if it's cold and it will just "click" and not engage.

Good luck with your project and let me know if you have any questions. That truck is a beast and will last you a long time. I have 250 XLT with 280k miles on it. The thing purrs right along and with the change to my battery connection and a new starter it starts like never before.

[muzzy1127]

I worked for ford for 11 years and am very familiar with the 7.3 powerstroke. I own 2 of them myself.

Are you positive the starter is hitting the flex plate? These motors need a ton of amperage to turn over. Check battery connections, and the conditin of the cables. They wont sell the new battery cables for the 99 anymore but it is the same from the 02.

A lot of the time the battery cables are corroded to the point that it causes a voltage drop at the starter.

Also Ive seen loose battery connections blow up batteries. my 7.3 excursion, for some reason goes through a set of batteries a year from blowing the post on the negative terminal off. Thankfully interstate has a good warranty program.

Start simple. Maybe put a volt meter on the battery youre cranking. It should NEVER drop below 10.8, or the IDM wont even fire the injectors.

[Sailor]

Not a ford or diesel guy, but my first impression from your post was electric, and most likely a grounding issue.

When do we get to see pictures of the 7.3 PS stuffed in the Mako 23? [][]

[DestinBound]

Sure sounds like it is hitting the flex plate, but I haven't caught it while watching. It is actually a fairly rare problem and has only happened back to back once since I've owned it (about 5 weeks). It will grind and next key turn is a normal start. Overall it has probably only happened maybe 5 times and I drive it everyday everywhere.

Batteries spin the engine over very well, no issues at all starting unless it decides to grind. I'd say its typically 3ish seconds to start cold or hot. Voltage is good, connections look good, but haven't taken anything apart yet.

I am leaning to an electrical issue too, just not an obvious one.

My '72 K5 loved to grind against the flex plate and it took a reduction gear starter to fix that one. Sounds the same to me but seamingly for different reasons.

Sailor - not looking to stuff one of those massive 7.3's into the Mako! That would be a fat boat for sure!!

We've had a bunch of Duramax's, a 6.0 Powerstroke, and a Cummins before. This is my first 7.3.

A pic:



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[muzzy1127]

nice truck!

Do you have any history on the transmission?

Simple start could just be the bendix not disengaging all the way.

The reason I asked about the Trans is that Ive seen in some instances people put aftermarket or beefed up torque converters. Sometiems even one from a 6.0 will fit Sometimes the crank spacer needs to be motified moving the flywheel closer to the starter. The starter may just need a shim or 2. I need to check in my notes but its a small shim like .10

[DestinBound]

quote:

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Originally posted by muzzy1127


nice truck!

Do you have any history on the transmission?

Simple start could just be the bendix not disengaging all the way.

The reason I asked about the Trans is that Ive seen in some instances people put aftermarket or beefed up torque converters. Sometiems even one from a 6.0 will fit Sometimes the crank spacer needs to be motified moving the flywheel closer to the starter. The starter may just need a shim or 2. I need to check in my notes but its a small shim like .10

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Thanks! No history on the transmission. After saying the issue was rare, I got a good taste of it yesterday morning. Three attempts in a row failed. When the issue happens the starter never engages at all. It just grinds. A spacer is a good idea. The starter could be on the edge of being too close to the flywheel. I did a quick google for the 7.3's flywheel to flange distance spec but Google didn't find anything for me.

Maybe you can find something in your notes that will give me something to look at.

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[muzzy1127]

ill look in my toolbox tonight. Most of the time you can see it, i leave the key off so it wont fire and just use one of those starter jumper wires with the buttom and play underneath til its right. Ive even seen some people grind a bit off the bendix.

Most of the time its reported after the trans has been rebuilt and theres been a modified torque converter, which is very common.

Id Almost get under there first and observe the bendix and see if it needs a shim (going to far) or a new starter if its not going far enough

[DestinBound]

Found a Ford technical bulletin on the issue and the answer, according to that bulletin, is to replace the starter with the updated one (2002+) and all is good.

Apparently it was common on "some" 1999-2001 models but not all.

The updated starter is very different and will require modification of the wring harness. Ford has a part# on that too, but looks like simple wiring change (longer) so should not be a big deal.

We'll see.

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[DestinBound]

Updated starter fixed the problem. [)]

Been chasing down oil leaks now. Man those 7.3's know how to leak themselves some oil. Replaced:

- Oil cooler o-rings

- Dipstick tube flange o-ring (replaced with part from Strictly Diesel expensive but works good)

- Oil pan ... the engine has to come out for this one so it will drip

The factory designed dipstick flange is not good. It was pouring oil due to an internal o-ring that is really painful to replace.

Also a few updates to quiet down the injectors:

- Fuel rail cross over

- Oil rail cross over

- Added friction modifier to oil change

Before all that #8 was hammering now purrs []

Fixing a few other miscellaneous things like the fuel pickup sucking air, suspension bushings, and glow plug relay set it straight. It has lots of miles, but is put together well and runs strong now.

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