IH PARTS AMERICA
Click Here!

Go Back   IH PARTS AMERICA > Tech Forums > Gas Engine Tech
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read Photo Gallery IH Store Home

Reply
 
Thread Tools Display Modes
Old 05-01-2012, 12:22 PM   #1
outlaw47
Junior Member
 
Join Date: Mar 2012
Member Number: 4516
Location: charleston,SC
Posts: 20
Default scout 80 unsteady vacuum and hard start

I have a '63 Scout 80 152 with about 250 miles on a fresh rebuild the problem I am having is more often than not it takes about 10- 15 seconds of solid cranking to start and then when it does it sounds like it is only firing on a couple cylinders but other times I look at the key and it fires up and runs great, once it is running it is great runs perfect I set the idle air screw using my ear and idle speed and that helped a little bit then I hooked up a vacuum gage and at idle with the vacuum side of the fuel pump disconnected it bounces between 16 and 20 in hg so am I doing this correctly does this indicate something is wrong?? Also my timing is around 15 degrees it seems to be happy there if I try to bring it to factory settings it gets very upset
outlaw47 is offline   Reply With Quote
Old 05-01-2012, 12:29 PM   #2
FDChappie
Senior Member
 
FDChappie's Avatar
 
Join Date: Aug 2011
Member Number: 3742
Location: Northern New California
Posts: 1,596
Default Re: scout 80 unsteady vacuum and hard start

I'd guess the problem is a sticking intake valve. Have you done a compression test?
FDChappie is offline   Reply With Quote
Old 05-01-2012, 04:52 PM   #3
outlaw47
Junior Member
 
Join Date: Mar 2012
Member Number: 4516
Location: charleston,SC
Posts: 20
Default Re: scout 80 unsteady vacuum and hard start

I have not done a compression test yet I will see if I have time to do one tomorrow but any idea why I could have a sticky valve I just rebuilt the head 250 miles ago?? Could my oil be to heavy (15w-40 rotella)??
outlaw47 is offline   Reply With Quote
Old 05-02-2012, 08:19 AM   #4
Robert Kenney
Super Moderator
 
Robert Kenney's Avatar
 
Join Date: Aug 2008
Member Number: 543
Location: So Cal
Posts: 3,411
Default Re: scout 80 unsteady vacuum and hard start

Quote:
Originally Posted by outlaw47 View Post
But any idea why I could have a sticky valve I just rebuilt the head 250 miles ago????
You bet! Bad fuel or new fuel put in a tank with old fuel residue.

Been there done that!

if you are against a good tank cleaning, add about 8 oz of atf to a full tank and take her out for a long road speed drive. You May see a bit of smoke now and then but the oil will lube the guides long enough to rid the tank of the old crud.

Your oil choice from a weight perspective is fine. Not much zinc but that's another story
__________________
Robert Kenney

“Don't lift until the fear of death over comes the fear of speed.” Author Unknown
Robert Kenney is offline   Reply With Quote
Old 05-02-2012, 09:12 AM   #5
FDChappie
Senior Member
 
FDChappie's Avatar
 
Join Date: Aug 2011
Member Number: 3742
Location: Northern New California
Posts: 1,596
Default Re: scout 80 unsteady vacuum and hard start

If a valve is what it is a good shot of marvel mystery oil is worth a try too.
FDChappie is offline   Reply With Quote
Old 05-02-2012, 11:32 AM   #6
outlaw47
Junior Member
 
Join Date: Mar 2012
Member Number: 4516
Location: charleston,SC
Posts: 20
Default Re: scout 80 unsteady vacuum and hard start

Ok I will give it a shot but I drained the tanks and replaced all the lines when I rebuilt the motor I have however been putting off cleaning and sealing them. I thought the oil I was using is high in zinc, what oil would be a better choice?
outlaw47 is offline   Reply With Quote
Old 05-02-2012, 05:01 PM   #7
Robert Kenney
Super Moderator
 
Robert Kenney's Avatar
 
Join Date: Aug 2008
Member Number: 543
Location: So Cal
Posts: 3,411
Default Re: scout 80 unsteady vacuum and hard start

One thing about a sticky valve, you'll almost certainly hear a tapping or ticking from exessive clearance.
While it is running rough, could you pull plug wirers and pinpoint the offending cylinder?
Oil wise the swepco product ihon sells is good. There are plenty of others that fit the levels. Most are special application oils like racing versions.
__________________
Robert Kenney

“Don't lift until the fear of death over comes the fear of speed.” Author Unknown

Last edited by Robert Kenney; 05-02-2012 at 05:07 PM..
Robert Kenney is offline   Reply With Quote
Old 05-05-2012, 07:23 AM   #8
outlaw47
Junior Member
 
Join Date: Mar 2012
Member Number: 4516
Location: charleston,SC
Posts: 20
Default Re: scout 80 unsteady vacuum and hard start

Ok a quick update I put some lucas top end lubricant and fuel system cleaner and have been running that through the tank I adjusted my air/fuel screw and timing a little bit and is starts much easier/consistently but still have very unsteady vacuum at idle once it hits 800-1000 rpm the vacuum is smooth. Using a stethoscope the valve train all the way across is nice and quiet I am still trying to find my compression tester (lost in the move) is there anything else that could cause the vacuum issue or is this even an issue? Also when I check the engine vacuum should I have the vacuum pump side of the fuel pump disconnected?
outlaw47 is offline   Reply With Quote
Old 05-05-2012, 06:50 PM   #9
Robert Kenney
Super Moderator
 
Robert Kenney's Avatar
 
Join Date: Aug 2008
Member Number: 543
Location: So Cal
Posts: 3,411
Default Re: scout 80 unsteady vacuum and hard start

You have the vac gauge hooked up to the intake tree/port in the center on the drivers side... Right? The same place the vac pump hooks up but no pump on that line?

We can't guess any further till you get a compression test done. Basically one hole is not pulling the same vac as the others. Not much that cen cause what you are seeing
pull the wires one by one and see which has the smallest decrease in rpm. That will the the offending cylinder.
__________________
Robert Kenney

“Don't lift until the fear of death over comes the fear of speed.” Author Unknown
Robert Kenney is offline   Reply With Quote
Old 12-14-2014, 06:19 AM   #10
Roughing it
Senior Member
 
Join Date: Jan 2013
Member Number: 5446
Location: Woodstock il
Posts: 124
Default Re: scout 80 unsteady vacuum and hard start

Having the same issue gonna run though some of these fixes. Thanks guys
Roughing it is offline   Reply With Quote
Old 12-15-2014, 06:33 PM   #11
Greg R
Senior Member
 
Join Date: Jul 2008
Member Number: 527
Location: Lebanon, OR
Posts: 793
Default Re: scout 80 unsteady vacuum and hard start

Quote:
the vacuum side of the fuel pump disconnected it
I have the same question as Robert. If you have vacuum wipers, the "vacuum" in goes to the wipers. The out goes to the manifold. For a good test, disconnect the vac pump at the manifold and take a vacuum reading at the manifold fitting.
Greg R is offline   Reply With Quote
Reply

Tags
1904, hard start, scout 80, vacuum

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -8. The time now is 09:59 AM.