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Everything new, still wouldn't start on it's own - SOLVED!

INFChief

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New York
66 M35a2, new to me
Starts on either and runs/drives good.
Idles around 900 rpm
when turned off, will not restart without more either.......
I have done the following:
Drained and cleaned fuel tank.
new in-tank fuel pump
all new fuel lines and filter relocate kit
new injectors
Fuel shut-off moves freely and is in the 7 o'clock position

Suggestions on what to check next?

thanx in advance
Oh, and did you replace the primary & secondary fuel filters?
 

Ferroequinologist

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Could be the HH going bad, had one do the same would run once you got it going but wouldn't build enough pressure while simply cranking it.

Have you tried running the intank pump for a minute before cranking? If it solves the problem, could be an air leak somewhere letting it loose prime.

Also, if you give it any throttle while cranking, will it start?

Did it have the same trouble prior to the new injectors?
 

Av3fire

Member
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Baltimore, Maryland
Could be the HH going bad, had one do the same would run once you got it going but wouldn't build enough pressure while simply cranking it.

Have you tried running the intank pump for a minute before cranking? If it solves the problem, could be an air leak somewhere letting it loose prime.

Also, if you give it any throttle while cranking, will it start?

Did it have the same trouble prior to the new injectors?

I have not tried letting the pump run for a bit, but will tomorrow
i have the pull throttle set at to about 1500 rpms to start it.... was told by the seller that is how you start it......
yes, had same problem before injectors and all of the work i have done...... i have been chasing ideas from here and other posts
 

Ferroequinologist

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I have not tried letting the pump run for a bit, but will tomorrow
i have the pull throttle set at to about 1500 rpms to start it.... was told by the seller that is how you start it......
yes, had same problem before injectors and all of the work i have done...... i have been chasing ideas from here and other posts
Unless letting the pump run a min lets it fire right up without having to touch the throttle,, I'd bet money it is a failing HH. I've changed over a dozen over the years, you are having all the common symptoms, after eliminating all the other possible causes.

You should be able to not touch anything and it fire up and idle at 750ish rpm. My last truck would start before I could squeeze the last air molecules out from between my finger and the button. Should have never sold it.
 

davidb56

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Bonners Ferry Idaho
Could be the HH going bad, had one do the same would run once you got it going but wouldn't build enough pressure while simply cranking it.

Have you tried running the intank pump for a minute before cranking? If it solves the problem, could be an air leak somewhere letting it loose prime.

Also, if you give it any throttle while cranking, will it start?

Did it have the same trouble prior to the new injectors?
I got a 1989 F450 7.3 that has been like that for 10 years now. Just give it a squirt of juice and off it goes. BTW my JD 4020 tractor manual states that you need to use ether in colder weather below 60F, and has a system similar to some of the deuce's with the screw in bottle and button.
 

Ferroequinologist

Resident railroad expert
Steel Soldiers Supporter
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Liberty Hill, SC
I got a 1989 F450 7.3 that has been like that for 10 years now. Just give it a squirt of juice and off it goes. BTW my JD 4020 tractor manual states that you need to use ether in colder weather below 60F, and has a system similar to some of the deuce's with the screw in bottle and button.
I'm familiar with other 7.3 like yours. He won't get 10 months out of the head if it is already this bad. And either is very hard on these real high compression engines. Sounds like it was failing on the previous owner, and who knows how long he ran it that way already.
 

Elk1111

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Las Cruces NM
Just for my own information..what exactly fails on a HH beside possible cracks in the head itself? Seems like most could be cleaned up without having to replace them.
 

G744

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Hidden Valley, Az
You might check compression, or have a shop test it for you.

A bit off, and they are hard to start. Even a newly rebuilt engine may not have the rings set in yet, and be hard to get going.

DG
 

frank8003

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When you replaced the pump did it come with a new pick up hose?
Yep, the second most important part. Hose must be for "immersed in fuel" use.
Otherwise it will entrain air.

My other thought was that You did many things at the same time. Question is did you save the "old" injectors?
Is the "new" injectors pop tested, do you have the numbers? Are the "new injectors the two hole type?
You could just put three of the old ones into #1, 3,+ 6 holes and try it. It is NOT a huge mess to pull any one of them and re-attach it to system and run it to a bucket and crank her. It is NOT a lot of fuel when cranking.
It is injectors or weak hydraulic head?
 

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frank8003

In Memorial
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The hydraulic head sleeve and rotating element is a very close fitting rotating part. The fuel filters are there to protect it. It is so finely hand lapped to be a perfect fit and crap in the fuel wears it fast. Think 5 micron clearance,
5 microns is 0.00019685inches.
The flow benches that were used to test the mechanism are all long gone.
What was the fuel the last owners were using in Her?
Study the hydraulic head.
There has been more than many threads here in Steel Soldiers about the HH.

post #81 in here
 

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Av3fire

Member
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Location
Baltimore, Maryland
Yep, the second most important part. Hose must be for "immersed in fuel" use.
Otherwise it will entrain air.

My other thought was that You did many things at the same time. Question is did you save the "old" injectors?
Is the "new" injectors pop tested, do you have the numbers? Are the "new injectors the two hole type?
You could just put three of the old ones into #1, 3,+ 6 holes and try it. It is NOT a huge mess to pull any one of them and re-attach it to system and run it to a bucket and crank her. It is NOT a lot of fuel when cranking.
It is injectors or weak hydraulic head?

had the same symptoms with the old injectors, this is why it was suggested to replace them.... cheaper first step than a HH
I am now beginning to think HH
the PO ran all kinds of crap in the fuel, 2" of sludge in the fuel filters bowls kind of crap

i'll look into replaceing the HH
 

Av3fire

Member
38
37
18
Location
Baltimore, Maryland
The hydraulic head sleeve and rotating element is a very close fitting rotating part. The fuel filters are there to protect it. It is so finely hand lapped to be a perfect fit and crap in the fuel wears it fast. Think 5 micron clearance,
5 microns is 0.00019685inches.
The flow benches that were used to test the mechanism are all long gone.
What was the fuel the last owners were using in Her?
Study the hydraulic head.
There has been more than many threads here in Steel Soldiers about the HH.

post #81 in here

I am thinking this too now
the PO ran all kinds of shit in the fuel
like 2"+ of sludge in the bottom of the fuel filters bowls

what do you guys think about getting a new HH?
are the aftermarket ones OK to use?
does it have to be an original one?
these seem hard to find and expensive (from a quick google search)

are they hard to replace? (I know the timing is super important, and i have never pulled one off...... afraid of turning the truck into a 9 ton lawn ornament!
 
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frank8003

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If you find for sale an original HH then Please let us all know where you got it.

see in a popular auction site
Hydraulic Head Injection Pump M35A2 2.5 ton Bosch PSB-6A

I had bought one as a spare and never needed it so sold it for like $200. I don't know if they be good or not.
Anyhow I put a 3 micron filter on Mine as never wanted to change all the other filters again and I wanted a clean tank and had a functioning perfect HH which I did not want to harm. I ran 90% NEW motor oil in Her and she liked it.
filter set IMG_4242.JPG
 
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