POP TESTING, NOT MUCH POP

Poorman · Jun 17, 2024

Working on my 1987 f350 6.9 with really bad smoke on startup. Injectors were replaced 8 years ago but I've only put 19,000 miles on them,(sits a lot). So I bought an injector pop tester and I'm trying to test them myself. They all hold pressure up to 1800/1850lbs but unless I really pump hard and aggressive they don't really pop, with a slow or even moderately fast stroke it looks more like an old man trying to take a leak. Good video's a scarce but it looks like they should pop even with a super slow stroke. What should I be seeing with these type of injectors? Thanks

rreegg · Jun 17, 2024

Not very experienced with injectors in general but a common procedure mentioned here is to fill the fuel filter with ATF or injector cleaner, start 'er up for a short duration and then let things sit overnight. Maybe they would benefit from being cleaned since they've sat

Attached below is the shop manual injector test section for a volvo marine diesel - to just have a visual representation. "RATT" is good and "FEL" is bad. I'd imagine things to be similar for the IDI injectors

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Poorman · Jun 17, 2024

rreegg, I think I'll try running some sea foam thru the pop tester, then let them soak for awhile, then flush them out with the pop tester, seams logical. I can then see if the spray pattern/opening/popping/pressure/anything changes. These don't have the 4seperate spray type pattern, they just spray straight, they're meant to do this.

The_Josh_Bear · Jun 20, 2024

Our injectors fire a straight line of fuel into the wall of the pre-chamber and the "splash" from that stream hitting the wall is what atomizes the fuel and then it can ignite evenly. Point is we have to have some pretty jacked up injectors for them not to work very well, since it's not atomizing the fuel in the first place.
As for the "pop", it's pretty subtle. The very first relief you feel is the pop. The biggest question with smoky start-up is "are the injectors leaking down?" For this you pressurize up to say 1600psi and wait a minute. If you get a drip or the beginning of a drip, then they are leaking down. You can always wait longer if you suspect them leaking. The ATF cleanse works well to clear up leak down, but as most things it's not going to fix everything.
The next item after that is timing the IP, and beyond that do a compression check. I recently did one after having harder starts and more smoke that I think I should for nearly 20 years...turns out I have low compression on one cylinder. But that's not gonna keep us out of the game!
:peelout

Poorman · Jun 20, 2024

Thanks for the response Josh Bear, I have done a compression test and it was pretty good 375/415. I can't get a couple of these to pop at all, they just squirt, the more I mess with them they seem to open with a weak squirt and then as the pressure is decreasing it just keeps getting a weaker and weaker stream down to 12-1300lbs to where it just dribbles a bit, they don't shut off abruptly like I'd think they should. It's like they open better than they close. Makes sense that this could be my problem, the weak stream wouldn't atomize when it hits the wall, it's more like a weak **** stream going in. Seem like that could cause the smoky start. When the motor gets hot it could easier handle liquid fuel and that's why it clears up and runs fine. I've been chasing this for several years, I didn't think it could be injectors because they were so new (19,000 miles). So I sent them up to Oregon fuel injection where I purchased them for testing, they got them yesterday so should hear back soon. I think they're a good company, they sure have great customer service. I'll post back.

KansasIDI · Jun 20, 2024

Poorman said:
Thanks for the response Josh Bear, I have done a compression test and it was pretty good 375/415. I can't get a couple of these to pop at all, they just squirt, the more I mess with them they seem to open with a weak squirt and then as the pressure is decreasing it just keeps getting a weaker and weaker stream down to 12-1300lbs to where it just dribbles a bit, they don't shut off abruptly like I'd think they should. It's like they open better than they close. Makes sense that this could be my problem, the weak stream wouldn't atomize when it hits the wall, it's more like a weak **** stream going in. Seem like that could cause the smoky start. When the motor gets hot it could easier handle liquid fuel and that's why it clears up and runs fine. I've been chasing this for several years, I didn't think it could be injectors because they were so new (19,000 miles). So I sent them up to Oregon fuel injection where I purchased them for testing, they got them yesterday so should hear back soon. I think they're a good company, they sure have great customer service. I'll post back.

This is how worn out injectors that smoke badly have pop tested for me

I’ll say the ATF trick does make a difference, fwiw

POP TESTING, NOT MUCH POP

Poorman

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rreegg

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Poorman

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The_Josh_Bear

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Poorman

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KansasIDI

I hate printers

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