compression numbers?? for a 7.3 IDI - Ford Truck Enthusiasts Forums



Pre-Power Stroke Diesel (7.3L IDI & 6.9L) Diesel Topics Only

compression numbers?? for a 7.3 IDI

Reply
 
 
 
LinkBack Thread Tools Search this Thread
  #1  
Old 05-26-2010, 12:19 PM
80broncoman 80broncoman is offline
Elder User
Thread Starter
 
Join Date: Nov 2003
Location: southeren Oh
Posts: 846
80broncoman is gaining momentum as a positive member of FTE.
compression numbers?? for a 7.3 IDI

I have a 89 7.3 IDI that has QUITE a few miles on it in a F-superduty rollback tow truck.
It is smoking slighty and I'm wondering just how close it is to needing a refreshening.
I know I have to buy the tester for a diesel, but what kind of compression numbers should I see on a 7.3??
Reply With Quote
  #2  
Old 05-26-2010, 11:43 PM
FORDF250HDXLT's Avatar
FORDF250HDXLT FORDF250HDXLT is online now
Post Fiend
 
Join Date: Jul 2006
Location: Maine/Oklahoma
Posts: 15,160
FORDF250HDXLT has a brilliant futureFORDF250HDXLT has a brilliant futureFORDF250HDXLT has a brilliant futureFORDF250HDXLT has a brilliant futureFORDF250HDXLT has a brilliant futureFORDF250HDXLT has a brilliant futureFORDF250HDXLT has a brilliant futureFORDF250HDXLT has a brilliant futureFORDF250HDXLT has a brilliant futureFORDF250HDXLT has a brilliant futureFORDF250HDXLT has a brilliant future
260-440 psi

the hynes diesel book states that if more than 20% variance is seen,and if there is a slight rough idle,the exhaust cam lobe could be the cause.
the compression should build quickly on a healthy engine.slow at first and slowly building pressure indicates worn rings.if it doesn't build up at all after the first stoke,this indicates bad valves/bad head gasket/cracked head,or carbon buildup on the valves.
you need to crank at least 6 compression strokes (listen for at least 6 "puffs") record your highest reading.

if compression varies greatly between cylinders,then you can have a shop pressure test the crankcase to pinpoint the problem.
if you see a couple low ones side by side,it can indicate a blown head casket between them.
Reply With Quote
  #3  
Old 05-27-2010, 07:36 AM
PLC7.3 PLC7.3 is offline
Post Fiend
 
Join Date: Nov 2004
Location: Manitoba
Posts: 5,638
PLC7.3 is gaining momentum as a positive member of FTE.
I have had up to 500psi........ 440 is very good, lowest must be 75% of the highest

Never use oil in the cylinders..... or it will hydrolock and bend a rod.
Reply With Quote
  #4  
Old 05-27-2010, 02:16 PM
Festus Hagen's Avatar
Festus Hagen Festus Hagen is offline
Methanoholic
 
Join Date: Mar 2009
Location: Maine (NorCal Native)
Posts: 6,443
Festus Hagen has a great reputation on FTE.Festus Hagen has a great reputation on FTE.Festus Hagen has a great reputation on FTE.Festus Hagen has a great reputation on FTE.Festus Hagen has a great reputation on FTE.
Quote:
Originally Posted by PLC7.3 View Post
I have had up to 500psi........ 440 is very good, lowest must be 75% of the highest

Never use oil in the cylinders..... or it will hydrolock and bend a rod.
You're not supposed to dump a cup in it, just a couple table spoons, it will not hydro lock on that!

-Enjoy
fh : )_~
Reply With Quote
  #5  
Old 05-27-2010, 03:14 PM
rodneywar's Avatar
rodneywar rodneywar is offline
Postmaster
 
Join Date: Jun 2009
Location: Maryland
Posts: 3,427
rodneywar has a good reputation on FTE.rodneywar has a good reputation on FTE.
Yea just a lil bit of oil to see if the rings are bad
Reply With Quote
  #6  
Old 05-27-2010, 04:48 PM
johnboggs21's Avatar
johnboggs21 johnboggs21 is offline
Posting Guru
 
Join Date: Jun 2008
Location: Michigan
Posts: 2,495
johnboggs21 is starting off with a positive reputation.
if its got real good compression it might just fire up and run on that oil lol
Reply With Quote
  #7  
Old 05-27-2010, 06:13 PM
IDIDieselJohn's Avatar
IDIDieselJohn IDIDieselJohn is offline
Post Fiend
 
Join Date: Feb 2009
Location: Ottawa, Ontario
Posts: 7,949
IDIDieselJohn has a great reputation on FTE.IDIDieselJohn has a great reputation on FTE.IDIDieselJohn has a great reputation on FTE.IDIDieselJohn has a great reputation on FTE.IDIDieselJohn has a great reputation on FTE.
Ever thaught about cleaning the CDR? Could be your smoke problem.
Reply With Quote
  #8  
Old 05-27-2010, 09:44 PM
80broncoman 80broncoman is offline
Elder User
Thread Starter
 
Join Date: Nov 2003
Location: southeren Oh
Posts: 846
80broncoman is gaining momentum as a positive member of FTE.
Quote:
Originally Posted by IDIDieselJohn View Post
Ever thaught about cleaning the CDR? Could be your smoke problem.
Right after I started this thread I read about the CDR. I'll defintly check into that.
Reply With Quote
  #9  
Old 02-26-2013, 02:38 AM
bajafishnut's Avatar
bajafishnut bajafishnut is offline
Posting Guru
 
Join Date: Nov 2005
Location: La Ribera, Baja, Mexico
Posts: 1,868
bajafishnut is a name known to allbajafishnut is a name known to allbajafishnut is a name known to allbajafishnut is a name known to allbajafishnut is a name known to allbajafishnut is a name known to all
7.3 Diesel compression numbers?

OK, I have read all the forum entries on 7.3 non turbo, compression, and not one entry gives any numbers?? How many pounds of compression is good? ok? needs rebuild?

My '93 F250 4x4 does not smoke, other than a small amount when starting, and runs fine. It does, and never has, gotten very good mileage. Like, 12 mpg on the average. I am running it now in Ca. which is suppose to have a cetain rating of 50 or so.. It has 220,000 miles, and seems to not have the power it once had... well duh, its getting older. I was wondering if I do a compression test, just how many pounds of compression should it have?
Reply With Quote
  #10  
Old 02-26-2013, 03:12 AM
kc0stp kc0stp is offline
Senior User
 
Join Date: Oct 2012
Location: Co
Posts: 333
kc0stp is starting off with a positive reputation.
Quote:
Originally Posted by bajafishnut View Post
OK, I have read all the forum entries on 7.3 non turbo, compression, and not one entry gives any numbers?? How many pounds of compression is good? ok? needs rebuild?

My '93 F250 4x4 does not smoke, other than a small amount when starting, and runs fine. It does, and never has, gotten very good mileage. Like, 12 mpg on the average. I am running it now in Ca. which is suppose to have a cetain rating of 50 or so.. It has 220,000 miles, and seems to not have the power it once had... well duh, its getting older. I was wondering if I do a compression test, just how many pounds of compression should it have?
http://www.ford-trucks.com/forums/12...sion-test.html

Frankly on yours Im thinking its more along the lines of timing/injectors/injection pump in need of adjustment/replacment
Reply With Quote
  #11  
Old 02-26-2013, 06:32 AM
bajafishnut's Avatar
bajafishnut bajafishnut is offline
Posting Guru
 
Join Date: Nov 2005
Location: La Ribera, Baja, Mexico
Posts: 1,868
bajafishnut is a name known to allbajafishnut is a name known to allbajafishnut is a name known to allbajafishnut is a name known to allbajafishnut is a name known to allbajafishnut is a name known to all
Injectors, timing, pump & more..

You are probably right, and I had thought of buying a new/rebuilt pump, but have decided to have the pump's pressure checked. I purchased the truck in 99 with only 37,500 miles on it, but noticed right away, that it would not keep up with my older '88 that had 220,000.

I had a rebuilt pump, (from the pump man in Redding Ca.), put on when I had 110,000 miles, but no new pump since then. I have however, put in new injectors, like, maybe... 3 times.. and used the Delphi brand, new from the box.

I use the truck as my Baja runner, and it makes 4 trips up and back annually. which is about 1000 miles each way. Its usually all pavement, other than washouts during the hurricane season. I have a K&N air cleaner, which I noticed someone made derogatory comments about ?? Is it not what I should be running? What then?

Perhaps its time for a pump, new injectors, and pump timing.. I will have it checked out. If you know a reputable diesel mechanic in the San Diego area, I would appreciate the turn oun..

thanks amigo,

Baja
Reply With Quote
  #12  
Old 02-26-2013, 01:30 PM
dsltech83's Avatar
dsltech83 dsltech83 is offline
Senior User
 
Join Date: Aug 2012
Posts: 111
dsltech83 is starting off with a positive reputation.
Quote:
Originally Posted by Festus Hagen View Post
You're not supposed to dump a cup in it, just a couple table spoons, it will not hydro lock on that!

-Enjoy
fh : )_~
It can start on that though, never do a wet test on a diesel. Leakdown is the best way to find out where your problem is.
Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
7.3 idi w/banks sidewinder EASTSIDEAUTO Pre-Power Stroke Diesel (7.3L IDI & 6.9L) 5 02-07-2012 03:25 PM
7.3 compression testing dieselaholic Pre-Power Stroke Diesel (7.3L IDI & 6.9L) 1 07-13-2011 01:52 AM
7.3 IDI Block heater part number? powerstrokedieselfan Pre-Power Stroke Diesel (7.3L IDI & 6.9L) 2 10-15-2010 05:13 AM
will a 7.3 idi diesel turbo work on a carburated 460 cowboy.2010 Supercharger, Turbocharger, Nitrous Oxide & Water/Methanol Injection 2 02-25-2009 01:15 PM
solid flywheel? pud Pre-Power Stroke Diesel (7.3L IDI & 6.9L) 57 10-19-2006 10:53 AM


Go Back   Ford Truck Enthusiasts Forums >

Tags
1989, 73, 73idi, 73l, bend, book, compression, diesel, engine, ford, idi, problems, psi, rod, smoking, test

Thread Tools Search this Thread
Search this Thread:

Advanced Search

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
Trackbacks are On
Pingbacks are On
Refbacks are On

Forum Jump


All times are GMT -5. The time now is 01:12 AM.


This forum is owned and operated by Internet Brands, Inc., a Delaware corporation. It is not authorized or endorsed by the Ford Motor Company and is not affiliated with the Ford Motor Company or its related companies in any way. FordŽ is a registered trademark of the Ford Motor Company.