I have a1989 ford f250 7.3 IDI engine that will crank but not start. Pretty sure the engine isn’t cranking fast enough to start. Just curious if there is a chance it has bad compression? Wondering what the signs would be of that. I am getting good fuel to the engine and bypassed glow plugs and they are working. Any advice is appreciated.
thanks

 

top of the page in the stickies, bottom post is how to tell a good starter from a bad starter.
two short videos. you can hear the difference.

 

Autozone sells reman starters w/ lifetime warranty for our trucks. I start my trucks multiple times throughout the day and I'v hardly had to swap them out over the years. I finally had to replace the one in the F450, though that one generally stays running on the job to keep the crane battery charged. They would have never known it didn't come out of my F250 but I'm too honest for that, so I bought one for that truck too. Same thing, AZ reman, since they're long lasting and free lifetime replacements!
I was looking back at my records and it looks like my first one in the F250 was a dud. It only lasted like a year....I don't even remember that. The next one several years though.......and that truck can get like up to 50 starts per day, moving around the job site....Well at least 20 to 30 starts during the day can be common. Point is, if they're lasting me, they'll last a guy who starts up his truck once to go to work and once to come home a very long time.


Oh, don't forget about the battery cables first. If they're 30+ year old originals........forgetaboutit. Time for new ones........Long past time for new ones haha. NAPA/ Traction can make them for you locally (what I always do for cables), or look for a set online. If you have them made and you can afford it, don't be afraid of up-sizing gauge either. If up-sizing; grounds needs to match (or be larger).

 

I’ve installed a new starter and it is cranking slow still. I’ve been charging the batteries is there a chance if the wiring isn’t the right gauge it won’t crank good?

 

if it is still cranking slow with new starter, either bad/dirty ground connections at block, bad connections at batteries, or corrosion inside the cables. closely look at the cables near terminal connections. if the jacket is split, look at the cable inside. if it is green, there is corrosion in there. sometimes you can get away with cutting the cable back and putting a new end on it, but usually you will need new cables.

 

Yeah, and to add to that, sometimes you'll see on the positive cables anyway, due to being red; A deep dark coloration, if not outright black to them. This often happens right around the battery terminals. That's another big tell, that inside, they're corroded heavy. The reason they turn black is because the corrosion is causing extra resistance and this causes heat.

If you see either of my or Tom description, do you know what will happen if you slice the cables open? Green powder will fall out everywhere hahaha You should have seen the ones on my F250 when I bought that truck.....Not pretty.

 

Check this out. Back when I got my first IDI truck, Dave, Tom (above) and some of the guys, got me going. I think you'll find it useful, because my truck had a whole bunch of small things that added up:

https://www.ford-trucks.com/forums/8...old-start.html

Wanna hear something cool? I've still never had to plug her in. I still don't know if that block heater even works.

This truck finally got hard to start again after all these years. I had to install another set of glow plugs, and my instant cold starts are back to where it was after fixing her up, back in '09.

 

Did it start and run before? Just won't start one day?
Having fast cranking is nice, but there is more to it.

 

The starter will start cranking gear but then after about 2-3 seconds will start to slow down. Does that entail that the cables are no good?

 

I have yet to still get it to start. The guy before said the engine was good and was going to sell it separate but I ended up buying the whole truck and had to rewire everything.

 

Sounds like weak batteries to me. What voltage do you read across the battery terminals? Do you have a battery load tester? If not, your auto parts store might be willing to test your batteries for you.
As to cables, the + terminal on pass side battery might be faulty. Do this first: Disconnect negative terminal on pass side battery and measure voltage between a big terminal on starter relay and a good ground. It should read EXACTLY the same as across driver side battery terminals directly.

 

yea, thar sounds like you have cable issues.

 

they are pretty new batteries both read over 12 volts with a volt meter. I have yet to check if the cable is faulty I will try that

 

You may want to check your starter relay as well. Jump 2 large terminals on the relay and see how it cranks. Then pull the thin wire off the relay and jump that small terminal to + on the battery or one of the large terminals on the relay with wire going to battery + and see if there will be any difference. Jumping 2 large terminals you are bypassing the relay. If no difference, check cables as I suggested earlier. If checks good, see the fat red wire going down to starter from the relay. Can't rule out bad ground too, so check voltage between + on each battery individually and chassis ground. I mean each by disconnecting + between them, but leaving ground cables connected. Voltage reading must be exactly the same as across battery terminals directly. Last thing would be starter itself.

 

between battery terminals reads 12.8 volts. Then I put voltmeter at the battery connect at the starter and crank for a few seconds and it goes down to about 6 volts.