Swapped 7.3 Engine- Won't fire!
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Junior User
Joined: Oct 2011
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Swapped 7.3 Engine- Won't fire!
So I swapped my engine - 1992 7.3 w/ 250,000 on it. When I took the head off, found a cracked valve, and the piston below it was shot with a cracked cylinder too.
Found a 1990 w/ 155,000 and put it in.
Got it all together, and trying to crank it this morning. It cranks, but no start.
Jumping the batteries to a running truck- reading 14.7v. Glow plugs seem to function as i voltameter test em as they're clicking and voltage goes up and down.
New fuel filter with clean fuel, bled bleeder til no air spurts. cracked the injectors several times to bleed air.
Still no start. White smoke is coming out of the air intake- indication of fuel, right?
Any ideas? I have my old injectors, glow plugs and IP... but would like to start it without swapping those over.
I don't know how the compression is on this engine.
The guy I bought it from put oil down the intake to keep it from seizing... could this be affecting it? Good or bad idea to try and pull start it?
Found a 1990 w/ 155,000 and put it in.
Got it all together, and trying to crank it this morning. It cranks, but no start.
Jumping the batteries to a running truck- reading 14.7v. Glow plugs seem to function as i voltameter test em as they're clicking and voltage goes up and down.
New fuel filter with clean fuel, bled bleeder til no air spurts. cracked the injectors several times to bleed air.
Still no start. White smoke is coming out of the air intake- indication of fuel, right?
Any ideas? I have my old injectors, glow plugs and IP... but would like to start it without swapping those over.
I don't know how the compression is on this engine.
The guy I bought it from put oil down the intake to keep it from seizing... could this be affecting it? Good or bad idea to try and pull start it?
i ain't rite
Joined: Mar 2005
Posts: 65,511
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From: Marlboro Mental Hospital.
if you have a manual trans, you can try pulling it. it is possible you have a weak starter, or weak batteries.
these engines need to spin over fast or they take forever to start.
are you getting any smoke out of the exhaust when cranking?
these engines need to spin over fast or they take forever to start.
are you getting any smoke out of the exhaust when cranking?
Lead Driver
Joined: May 2011
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ugh. . .the previous owner poured oil down the intake!?!?!? 
he gets 3 spanks for that. he deserves more than that. . .
pouring oil down the intake could yield horrible results, like bent rods, broken pistons, and mangled valves (dejavu for you?)
hopefully he didn't pour enough down there to cause such damage. if it were my motor, i'd start with a compression test to make sure that the platform is even worth your time. the compression test isn't just to diagnose your current issue, although it will eliminate broken innards as a possibility, but also to give you peace of mind from now on knowing you started with a worthy candidate.
tugging it is a great idea, helps with trapped air pockets as well (I've had to tug my vp truck a time or 2 after the pump cavitated from letting off hard after a hard rip) however, shouldn't be done until it is confirmed there is no fluid in the cylinders. a slow crank could be a symptom of fluid in there as well....
he gets 3 spanks for that. he deserves more than that. . .
pouring oil down the intake could yield horrible results, like bent rods, broken pistons, and mangled valves (dejavu for you?)
hopefully he didn't pour enough down there to cause such damage. if it were my motor, i'd start with a compression test to make sure that the platform is even worth your time. the compression test isn't just to diagnose your current issue, although it will eliminate broken innards as a possibility, but also to give you peace of mind from now on knowing you started with a worthy candidate.
tugging it is a great idea, helps with trapped air pockets as well (I've had to tug my vp truck a time or 2 after the pump cavitated from letting off hard after a hard rip) however, shouldn't be done until it is confirmed there is no fluid in the cylinders. a slow crank could be a symptom of fluid in there as well....
Elder User
Joined: Jun 2012
Posts: 650
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From: Plant city florida
Can oh please go in depth on how the oil in the intake can cause damage?(genuinely asking that). We have a 2001 Honda rancher 350 2x4 4wheeler and I let this kid ride it at the local mud hole, he flipped it In water yada yada long story short drained and changed gas with water In it to clean gas, did a few oil changes(still milky) and when we *finally* got it to run it ran all the watery oil out of the intake and smoked like it didn't even have rings til it was all gone then didn't smoke at all. I know it's TOTALLY different but considering there was no more obvious damage than before I don't see what damage it could even do ?
Postmaster
Joined: Dec 2011
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Two potential issues: One, hydrolocking - water(and oil) can't be compressed. You get too much in the cyl and it has to go somewhere very quickly == something breaks.
Two, heat. Oil burns quite hot. Our 7.3s tend to suck a bit of oil in through the CDR valve, which is at the back of the engine. The rearmost cyls run hotter because of it. I'm thinking, therefor, that if you burn oil in the engine, you're probably ending up with it being hotter than otherwise.
Personally, I'd say that it's probably not as bad as it seems; disable your glowplugs and put a smidge of ether in there. Ether isn't good for these engines(especially the GPs), but a little bit will start a truck right up, even if the timing is way off etc.
Don't just pour it in there, but just a smidge... see if it helps.
Two, heat. Oil burns quite hot. Our 7.3s tend to suck a bit of oil in through the CDR valve, which is at the back of the engine. The rearmost cyls run hotter because of it. I'm thinking, therefor, that if you burn oil in the engine, you're probably ending up with it being hotter than otherwise.
Personally, I'd say that it's probably not as bad as it seems; disable your glowplugs and put a smidge of ether in there. Ether isn't good for these engines(especially the GPs), but a little bit will start a truck right up, even if the timing is way off etc.
Don't just pour it in there, but just a smidge... see if it helps.
Lead Driver
Joined: May 2011
Posts: 5,776
Likes: 443
Can oh please go in depth on how the oil in the intake can cause damage?(genuinely asking that). We have a 2001 Honda rancher 350 2x4 4wheeler and I let this kid ride it at the local mud hole, he flipped it In water yada yada long story short drained and changed gas with water In it to clean gas, did a few oil changes(still milky) and when we *finally* got it to run it ran all the watery oil out of the intake and smoked like it didn't even have rings til it was all gone then didn't smoke at all. I know it's TOTALLY different but considering there was no more obvious damage than before I don't see what damage it could even do ?
small motors have a good bit of overlap in the cam, which eases the stress of fluid in the combustion chamber. if theres enough fluid in there, damage will still be done, but chances are minimized due to the overlap (its also just one cylinder, vs 8 prospects for failure in the op's case).
if the piston moves up, and there is enough fluid to get trapped between the piston and the head, something will give. . .period. often times, it results in broken pistons, rings, and mangled rods.
Elder User
Joined: Jun 2012
Posts: 650
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From: Plant city florida
in your case, the excess smoke was the oil/water/gas mixture burning out of the exhaust, burning the same mix out of the combustion chamber, and pulling gunk of the carb-also yielding smoky results. believe me, damage was done. it may not have been catastrophic, but your friend took life off of your quad's motor. how much? impossible to tell, but rings and cylinder walls don't like the stress, and bearings/rings/cylinder walls/carbs don't like water. no sense in worrying about it though. rock it til it stops, which will most likely be many years.
small motors have a good bit of overlap in the cam, which eases the stress of fluid in the combustion chamber. if theres enough fluid in there, damage will still be done, but chances are minimized due to the overlap (its also just one cylinder, vs 8 prospects for failure in the op's case).
if the piston moves up, and there is enough fluid to get trapped between the piston and the head, something will give. . .period. often times, it results in broken pistons, rings, and mangled rods.
small motors have a good bit of overlap in the cam, which eases the stress of fluid in the combustion chamber. if theres enough fluid in there, damage will still be done, but chances are minimized due to the overlap (its also just one cylinder, vs 8 prospects for failure in the op's case).
if the piston moves up, and there is enough fluid to get trapped between the piston and the head, something will give. . .period. often times, it results in broken pistons, rings, and mangled rods.
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Okay got it started...
It is overheating. Is there a process of "burping" the coolant system if it was all empty? Where is the thermostat, so I can check that?
It is overheating. Is there a process of "burping" the coolant system if it was all empty? Where is the thermostat, so I can check that?
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Joined: Mar 2005
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From: Mexico, Missouri
Just wanted to know what you did to get it started? Also, your new post noted its dying going uphill and this post that its overheating. Not a diesel mechanic, but sounds like a stuck shut thermostat.
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But yeah, during the test drive the gauge never got into normal (I know this doesn't really mean anything), but the hoses were all really hot, and the truck died up a hill..
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https://www.ford-trucks.com/forums/1...l#post13457238
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