Another 7.3 idi won't start thread... I'm sorry...

[Ryan Nunez]

Hey all, I'm sorry in advance for making another one of these threads but I can't seem to piece other ones together to solve my issue(s). I recently bought a 93 f250 7.3 idi NA and it runs extremely well. The problem is that I now can't get it to start. It was running when I got to the guys house to look at it and at one point I shut it off and when I went to leave with it after it had been sitting for roughly half an hour, it would not start. The guy said that he knew it was pretty low on fuel (gauge is broke) and with the way the truck was sitting it might not be getting fuel. I bump started it (in reverse no less) and it fired instantly and ran great to the gas station and fired up fairly quickly after I filled it up.

Fast forward to the next day when I wanted to move it to start doing work on it and it would crank and not start. It did start after I had it plugged in overnight and hooked up to my van with jumper cables. Ran pretty rough for a few minutes then leveled out and ran fine. Parked it for an hour and it started up no problem. Now I'm having the same problem with it not starting again the next day. I checked fuel at all 8 injectors and at the shrader valve. I had both batteries tested that resulted in ~12.5v and 850 CCA. My FSS clicks like it should when I remove power with the key on.

I tested the resistance to the negative of all 8 plugs, 6 of them were 1ohm and 2 were 2ohms. I am assuming the 2 that tested higher are bad. The guy I bought it off of said he changed the glow plug relay and the glow plugs (Autolite... I know...). The relay holds as designed for 4-5 seconds and then when the WTS light goes out you can hear the relay clicking and I'm assuming it is because of the two bad plugs. I did wire in a manual switch for the glow plugs as suggested on other threads on this site and even with the extra time, it still won't start however I did not have it plugged in last night.

Are these two glow plugs enough to stop the truck from starting on a 50 degree day? Is there something that I am missing? Any help would be greatly appreciated. I have had multiple diesels in the past but this is my first IDI.

 

[Cubey]

It's probably air intrusion in the return lines. That's the biggest starting issue on these things.

The rear most soft return line over the C6 bell housing on my RV was so bad that it had to be replaced before it could even run when I bought it. The seller had to go get a piece of hose from the auto parts store before I could drive away with it. Then it started and was ok, for about a month.

Then the o-rings gave up finally and I had to replace them. I was expecting it, so it was no shocker to me. My F250 was the same way. Was fine for about a month then needed o-rings.

Later on, the soft line at the mechanical lift pump it had at the time (now has electric) was leaking and causing air intrusion there. Once that was fixed too, I've never had air intension problems again, even when the mechanical lift pump was weeping (seal failing).

 

[Ryan Nunez]

That is something that I had read and was trying to check. I traced all the return lines and none of them were cracked and I wasn't able to find any fuel leaks from when I had it running yesterday. Is there a good way to be sure this is the problem? Will this stop the truck from starting even if all the injectors are getting fuel

Thank you so much for your reply, I love that everything on this truck is "simplified", but for someone that is used to changing sensors to fix their problems this is a whole different animal haha

 

[miles1400]

i believe all the glow plugs should be reading less than 1 ohm, therefore all of your glow plugs are bad. i recommend you replace them with Ford Motorcraft ZD-9 glow plugs, they are the best ones you can get and you can find them online.

depending on how long you were having the plugs glow with a manual switch you might have burnt them out, i have heard of it happening before.

once you get the glow plug problems sorted out you should fix any air intrusion problems, most common spots is the return lines and the fuel heater in the filter head. once you have good glow plugs and an air tight fuel system your truck should fire right up even in the middle of winter

 

[Ryan Nunez]

Thank you Miles. I actually have already ordered the new Mastercraft glow plugs... Along with, oil, oil filter, coolant, sca additive, test strips, after market temperature gauge, and a thermostat ( its running pretty hot and I think that the thermostat is stuck closed).

I agree with your concern about the manual switch burning out the glow plugs but I have only engaged them manually for 7 seconds at a time then cranked the engine. Then I let everything sit for a few minutes when it doesn't start because I don't want to put extra strain on the starter.

Guess its time to get back on Amazon and order the return line kit!

 

[miles1400]

@Ryan Nunez Napa should have them in stock, and if you are a AAA member and show them the card you get 10% off your purchase

 

[Ryan Nunez]

@miles1400 They should have the glow plugs or the return line kit?

 

[miles1400]

@Ryan Nunez return line kit

 

[Cubey]

That is something that I had read and was trying to check. I traced all the return lines and none of them were cracked and I wasn't able to find any fuel leaks from when I had it running yesterday.

It can be hard to see since the leak at the o-rings/caps can be very small. And when running I'm not sure you can hardly see it even. The o-rings might swell with heat and not leak when running. Sitting cold overnight may shrink them and let in air.

Did you check the soft line on the back by the bell housing? It's buried deep on trucks and is easy to miss. It's way easier on vans since you can get right to the back of the engine. The green line is it:

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[Farmer Rock]

Since it starts good with the block heater,it isn't air intrusion causing this.The variables in this case are obviously the GPs,then the starter and batteries.Make sure the batteries are fully charged,and that the starter is turning over nice and fast.Check all your cable connections,as they can easily be corroded causing the starter to turn too slow or the starter could be weak.Sounds like the guy had it running a while before you got there,and you said it started right up when bump starting it,so all of this points to the starting system if you ask me.If it was the GPs,it still should have started easily if it was still hot,and if it was air intrusion,It wouldn't start right up just because the block heater was plugged in.I would be looking at the starter.



Rock

 

[Ryan Nunez]

@Cubey i did trace the feed and return lines back to the tank and couldn’t find any clear issues with them but I am going to give them another try while I wait for the parts to come in Sunday (gotta love amazon prime)

@Farmer Rock , I’m almost at the point where I think that it starting yesterday with the block heater plugged in was a fluke and I just caught it at the right amount of cranking and mashing the throttle. Once it finally caught and started I had to keep feathering the throttle to keep it running and I’m of the assumption that was because of the air in the system. With that being said I am already committed to changing both the glow plugs and the fuel return lines to cover all the bases since the return line kit is inexpensive. I’m sure I’ll be cussing the whole time I’m trying to prime everything with my wife who doesn’t even know what the third pedal is for in the drivers seat “helping” me

 

[Ryan Nunez]

@miles1400 nice, I’ll call them tomorrow and if they do I’ll grab that and cancel my order. Thanks!

 

[Cubey]

@Cubey i did trace the feed and return lines back to the tank and couldn’t find any clear issues with them but I am going to give them another try while I wait for the parts to come in Sunday

It's 5/16" fuel line, so it's cheap enough to just replace if it looks old. (The hose between injectors is smaller, 3/16" as I recall?) Speaking of which, I need to find that tiny section of line I spotted that's original from 1985 right after that green line section (towards the tank). Why it has another soft line so soon, I dunno.

 

[Selahdoor]

Replacing the glow plugs and the return lines are both good things to do.

The next time that you try to start it, pay attention to how fast your engine turns over. I have a hunch you may need to replace the batteries and/or the alternator. They may not be turning the engine over quickly enough, or strongly enough.

If you replace the batteries, replace both of them, not just one. Replacing just one only SEEMS cheaper. The other old battery will soon drag down the new one.

 

[Cubey]

I have a hunch you may need to replace the batteries and/or the alternator.

Before replacing either, if it has the gen 1 style alternator, make sure the two wire plastic connector isn't wiggling out from the alternator. My RV's has a weak plastic "spring" that holds it in. I ran a small zip tie around the connector but under the "spring" and pushed the connector back in, and that helped enough that it hasn't ever wiggled back out on it's own in well over a year and several thousand miles. A piece of gorilla tape would also work. Just anything to hold the connector down. If that isn't connected properly, the alternator won't do any charging.