Engine stops running

nickb2

Wrench. Diagnostic Tech.
Joined
Nov 22, 2008
Messages
8,868
Likes
154
Points
63
Location
St-Hyacinthe, Quebec, Canada
#16
Thx for sharing that info. Very informative article and well written.

The younger guy's at the shop laugh when I pull out my vac gauge. It is older than me. It was given to me by an old mentor of mine when he retired. I would always go for his gauge since he was the one who actually taught me how to read an engine with a vac gauge.

That does take experience. I used it just the other day for a 5.4l ford engine, great money makers for us techs. Anyway, I knew the timing chain case was going to be a goner as well as the phazers etc. Everything was grinding and whining, but I wanted to know if the base of the engine was sound and vac told me that. Held steady @18-20. Was hard to talk with the others guy so much this engine was howling no serpentine to prove every was going to hell in the front of that timing case, but it was sound. I didn't want to take comp reading, would not have been reliable with timing system loose like that at starter speed, would have gotten maybe a false sense the base was shot also.

I will tear into the front on monday, client gave me the go ahead. It was that or a swap. But try and find a good 5.4l 3valve left in the salvage yards. There all gone. What a shytty engine ford did with that one. 23hrs book time to swap a short, 12hrs just for the timing system. That doesnt include checking the cams if they are worn and replacing the phasers.

Anyway, all this to say that a vac guage is one of the most under used diagnostic tools that just stands the test of time and requires no scanner or wifi.:cool:
 
Last edited:

cw41

Hero Member
Joined
Nov 21, 2006
Messages
518
Likes
4
Points
18
Location
Arizona
#17
that is an absolute awsume article on this subject. I'm going to see if the site will let me print it out!! I imagine thats not a problem. Yesterday I thought that the IAC was the culprit and it started , idled and ran just fine, drove all around the neighborhood within walking distance of my house. i thought the black cat was fixed. this morn it was about 20 deg and went outside and started right up, ran back in for 15 minutes and the car had stalled out at about half way up on temp according to the gauge in dash. shut the key off and it wouldnt start again. almost set it on fire right there. Its been suggested that I look closer at the egr and block it and try then. Its original to the car so after 134,000 its probably not in the best shape. thank you again for the above article. Very well done!!!
 

grcauto

Hero Member
Joined
May 29, 2014
Messages
301
Likes
19
Points
18
#18
Thx for sharing that info. Very informative article and well written.

The younger guy's at the shop laugh when I pull out my vac gauge. It is older than me. It was given to me by an old mentor of mine when he retired. I would always go for his gauge since he was the one who actually taught me how to read an engine with a vac gauge.

That does take experience. I used it just the other day for a 5.4l ford engine, great money makers for us techs. Anyway, I knew the timing chain case was going to be a goner as well as the phazers etc. Everything was grinding and whining, but I wanted to know if the base of the engine was sound and vac told me that. Held steady @18-20. Was hard to talk with the others guy so much this engine was howling no serpentine to prove every was going to hell in the front of that timing case, but it was sound. I didn't want to take comp reading, would not have been reliable with timing system loose like that at starter speed, would have gotten maybe a false sense the base was shot also.

I will tear into the front on monday, client gave me the go ahead. It was that or a swap. But try and find a good 5.4l 3valve left in the salvage yards. There all gone. What a shytty engine ford did with that one. 23hrs book time to swap a short, 12hrs just for the timing system. That doesnt include checking the cams if they are worn and replacing the phasers.

Anyway, all this to say that a vac guage is one of the most under used diagnostic tools that just stands the test of time and requires no scanner or wifi.:cool:
It is rather odd that very few teachers will discuss the vacuum gauge and it's wealth of information and ease of use. I've seen these guys doing contortionist type maneuvers trying to get at a front O2 sensor and then breaking everything except the grip the threads have on the bung and they are just wanting to see if the exhaust is plugged. I ask....'do you have a vacuum gauge or pump'....I think I've seen one of those things around somewhere......Do you think you can find it quicker than getting that O2 sensor out.......Let me see.......a couple minutes later he comes with a MityVac, I ask him to start the engine. I connect the gauge to the intake and run the rpms up to 3000 and hold it there for 10 to 15 seconds and let my finger off the throttle and the gauge goes up several inches and drops back down to normal......I tell him the exhaust is not the problem,,,,,,,He just thinks, I never heard of this that proves nothing to me, ..so.....continues to remove the O2 sensor. Starts the vehicle and still had the low power and lag.....His face is beat red as he goes to install the removed O2 sensor. This was a GM MAF 3.1 or 3.8 L engine. At any rate he gets the O2 back in place and starts starring at the engine. I asked about the fuel pressure which was good and held steady during the events. I asked if he checked the datastream and looked closely at those pid's used in fuel calculation.....Oh yes, they seem fine. I looked at the trims and MAF as well as the O2's I noticed the MAF seemed to be a little flaky. I got out of the vehicle and while it was idling I took a screwdriver and tapped on the MAF and the vehicle stalled. I told him to replace the MAF.
He was a tech with about 2 years experience and thought he knew it all. I think if I'm being honest I was that tech about 15 years earlier. At any rate it gave me the opportunity to show him the value of old school techniques on modern vehicles. The tap test on GM MAF was something I had learned from a GM master a few years earlier. He taught me that if you get a GM vehicle in your bay that uses MAF you always want to tap them and if they stall they are bad. PERIOD. He told me they may not be back right away but if they fail that tap test they will be back before to long. Just tell the customer and let them make the decision. He was right.
Experience is a great teacher and it's great to learn from those who have spent the time learning and are willing to pass that down to the next generation.