DIY: Harbor Freight $30 Compression Tester Easily Modded for Success!

BDCarrillo

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I do know a few threads on this forum mentioned that the cheap Harbor Freight kit could be modified, but details were lacking...

First common complaint: Stuck gauge or air bleed doesn't work. Note that the bleed is depressed in the photo below. I'm not sure what kind of valve it is, but giving the bleeder several stiff whacks (with something like the pictured clamp) will depressurize the gauge. I suppose you're fighting the built-up internal pressure of the gauge assembly.
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Second common complaint: The adapter listed for the 6.9 or 7.3 IDI doesn't work. Out of the box, this is true. However, by removing the valve core, trimming it to length, chamfering the end, and replacing the valve core it will work. I used a 1" belt sander to grind it down to length (about 1/4" removed) and then chamfered the edges with sand paper. Make sure to blast it out with air before replacing the valve core. Start slightly longer than the numbers in the photo and work it down to size, just to be safe.
You must be registered for see images attach


For comparisons sake, my modified $30 kit adapter, a Beru glowplug, and the $130 kit adapter, all aligned by the shoulder which seals them to the head.
You must be registered for see images attach



Compression test procedure:
1: Remove air filter assembly
2: Disconnect glow plug relay (white wire shown below, ziptied out of the way)
You must be registered for see images attach

3: Disconnect Fuel Shutoff Solenoid (connector towards front of vehicle, on top of injection pump, drivers side)
You must be registered for see images attach

4: Disconnect and remove glow plugs with a 3/8" deep socket. Many have reported that it's easier with 1/4" drive sockets. (difficulty may vary based on engine year/turbo)
5: I opted to make a "bump starter" that energizes the starter relay. This can be done with a momentary switch connected between the battery positive and small post on the relay. This allows you to stand in front of the engine and observe the gauge directly. See photo
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6: Install adapter in glow plug hole, gently snug down.
7: Attach gauge. I opted to secure it with a small clamp.
8: Energize starter relay, allow to crank 6-8 revolutions. Be consistent and use the same number of revolutions per cylinder tested.
9: Record pressure, gently whack silver bleeder below the gauge. It will pop briefly at higher pressures, then drain normally at lower pressures.

Repeat 6-9 for each cylinder. Numbers WILL vary... a variance of 20-25% OR 40 psi between the highest and lowest has been considered the "norm" from other threads on here... use your judgment or post up your own thread with your numbers. Similarly, reported numbers have varied from mid 200's to mid 400's. Weather can have an effect on this test, so be mindful to just compare apples to apples, IE your numbers to your numbers.

Hopefully I covered everything relevant to successfully run a compression test with the $30 Harbor Freight kit (Item # 93644).
 

NO_SPRK

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fyi i have the $130 black adapter and yes it does work but goodluck getting the fitting to snap on.. no space
 

BDCarrillo

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fyi i have the $130 black adapter and yes it does work but goodluck getting the fitting to snap on.. no space

I didn't have any issues getting the modded cheapie adapter hooked up on my 92 7.3 N/A motor. Not a single hitch accessing all glowplug holes, even those under the fuel lines.
 

OLDBULL8

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This is the HF tester I've got, 1st pic and 3rd pic with the P/N on the cover. the 2nd pic is the cheap one. The 1st one does have the adapter that will work, but the 90* gauge connector is difficult to get on the adapter. The GP threads are 10.01 mm which is close to a 1/8" pipe thread, so I use a 1/8"x 6" nipple a 45* and a 1/8" x 2" nipple with a female quick connect on the end. The pipe metal is soft enough it won't damage the GP threads.

I see HF has reduced the amount of adapters since I bought mine, probably back in 06 or before, same P/N #.
IIRC I paid $39 at that time.

All in all, that's a good mod to the adapter you did.

By the way, any PSI from 350 to 450 is within spec. Some have said they have over 500.
 

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NO_SPRK

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I didn't have any issues getting the modded cheapie adapter hooked up on my 92 7.3 N/A motor. Not a single hitch accessing all glowplug holes, even those under the fuel lines.


well look at the difference between the chrome $30 one and the black $130 one. the head is a air line fitting. much bigger i borrowed the black adapter and used a air line fitting on my compression gauge. could not get it to hook up on all the cylinders

the one in the $130 kit looks bigger than the older $30 kit
 

ToughOldFord

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FWIW I got the cheap kit about a year ago, sure enough didn't work. Returned it and got the expensive one, worked fine and I had no trouble checking all 8 on my '86 6.9

Good to know the cheaper one can be modified though, that'll save some guys some $$$
 

BDCarrillo

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I hate to bring back an older thread of mine but if anyone else concurs, I think it ought to be in the tech section...
 

VanDiesel

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Glowplug Compression Adapter Mod for 7.3

From the comparison picture, it looks like the schrader valve now sticks out instead of screwing in all the way, and that the length allows a few threads to engage, but not all. Is this the case, that it couldn't be cut down and allow the valve to be screwed in all the way?


I do know a few threads on this forum mentioned that the cheap Harbor Freight kit could be modified, but details were lacking...

First common complaint: Stuck gauge or air bleed doesn't work. Note that the bleed is depressed in the photo below. I'm not sure what kind of valve it is, but giving the bleeder several stiff whacks (with something like the pictured clamp) will depressurize the gauge. I suppose you're fighting the built-up internal pressure of the gauge assembly.
You must be registered for see images attach


Second common complaint: The adapter listed for the 6.9 or 7.3 IDI doesn't work. Out of the box, this is true. However, by removing the valve core, trimming it to length, chamfering the end, and replacing the valve core it will work. I used a 1" belt sander to grind it down to length (about 1/4" removed) and then chamfered the edges with sand paper. Make sure to blast it out with air before replacing the valve core. Start slightly longer than the numbers in the photo and work it down to size, just to be safe.
You must be registered for see images attach


For comparisons sake, my modified $30 kit adapter, a Beru glowplug, and the $130 kit adapter, all aligned by the shoulder which seals them to the head.
You must be registered for see images attach



Compression test procedure:
1: Remove air filter assembly
2: Disconnect glow plug relay (white wire shown below, ziptied out of the way)
You must be registered for see images attach

3: Disconnect Fuel Shutoff Solenoid (connector towards front of vehicle, on top of injection pump, drivers side)
You must be registered for see images attach

4: Disconnect and remove glow plugs with a 3/8" deep socket. Many have reported that it's easier with 1/4" drive sockets. (difficulty may vary based on engine year/turbo)
5: I opted to make a "bump starter" that energizes the starter relay. This can be done with a momentary switch connected between the battery positive and small post on the relay. This allows you to stand in front of the engine and observe the gauge directly. See photo
You must be registered for see images attach

6: Install adapter in glow plug hole, gently snug down.
7: Attach gauge. I opted to secure it with a small clamp.
8: Energize starter relay, allow to crank 6-8 revolutions. Be consistent and use the same number of revolutions per cylinder tested.
9: Record pressure, gently whack silver bleeder below the gauge. It will pop briefly at higher pressures, then drain normally at lower pressures.

Repeat 6-9 for each cylinder. Numbers WILL vary... a variance of 20-25% OR 40 psi between the highest and lowest has been considered the "norm" from other threads on here... use your judgment or post up your own thread with your numbers. Similarly, reported numbers have varied from mid 200's to mid 400's. Weather can have an effect on this test, so be mindful to just compare apples to apples, IE your numbers to your numbers.

Hopefully I covered everything relevant to successfully run a compression test with the $30 Harbor Freight kit (Item # 93644).
 

BDCarrillo

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From the comparison picture, it looks like the schrader valve now sticks out instead of screwing in all the way, and that the length allows a few threads to engage, but not all. Is this the case, that it couldn't be cut down and allow the valve to be screwed in all the way?

The schrader valve does stick out, and has to. The threaded part the schrader valve screws into is not very deep, and it's a unique flared seat that would be hard to cut deeper into the adapter. There area few workarounds if you want to shorten the adapter to get more thread engagement (and do away with the schrader valve). Without the schrader valve, compression is released when the valve opens.

1- Install a one-way valve that keeps the gauge pressurized
2- Use a gauge that records a maximum reading
 

cpdenton

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After reading this, I decided to give the HF tester a shot. Turns out, some things have been redesigned. The fitting no longer has a schrader valve in it. It is still too long, and needs to be shortened, but is a straight through design now. I have tested two cylinders so far and the pressure release valve seems to work as it should.

I will post up some pictures tomorrow.
 

Selahdoor

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I know this is old, but there really is a cheap, effective tester to be had at HF.

This one: https://www.harborfreight.com/compression-test-kit-8-pc-62638.html
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That adapter at the top right there, will screw right into the glow plug hole. No problem.

Then the hose screws into the adapter. The schraeder valve is in the end of the hose, not the adapter.

Yes, it still has a problem letting go of the pressure with the button on the side, but you can reach in and depress the schraeder valve in the bottom of the hose, with a small screwdriver.

Last... The gauge only goes to 300 pounds. But you can get an excellent quality replacement gauge that goes to 600 or 1000 on amazon. Very easy to replace that gauge.

The kit is $27.00. Add in the replacement gauge, and for less than 50 bucks you'll have a compression tester that works and works well.
 
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Reggie f250

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Just bought the pittsburgh compression tester item 62594 it looks different from the others. Havent tried it yet. Hope to soon.
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Selahdoor

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Just bought the pittsburgh compression tester item 62594 it looks different from the others. Havent tried it yet. Hope to soon.
You must be registered for see images attach
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Does the fitting have the schraeder valve in it? Or is the valve in the end of the hose?
 
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