IO-360 frequent blocked injectors

[m100psi]

Hi all,

I know injectors get blocked occasionally, but I've had 4-5 blocked or partially blocked injectors since picking up my M20J in November last year. 

Before picking it up, I had a full chemical strip and reseal done on both tanks.  Since then, besides several injector cleanings, I've had the gascolator and fuel servo screens cleaned.  Both had gunk in them before cleaning. Since I've had more blocks since then I'm going to get those screens checked/cleaned again, but I wondered where downstream of these stuff might be getting dislodged from?

Thanks,
Matt

 

[carusoam]

Matt,

One important place to look, for the J...

There is a ‘rubber’’ fuel hose related to the fuel injection system that has been known to have the inner surface stuff off...

Sounds like you may want to look into that...

It has been detailed around here before.

Let us know if you need help finding the details...

Frequent blocking of FIs is not normal...

Best regards,

-a-

[ArtVandelay]

There is a fix for dying boost pumps coming apart, my J has a screen after the boost pump to catch any debris. Did you check it?

[PT20J]

8 hours ago, ArtVandelay said:

There is a fix for dying boost pumps coming apart, my J has a screen after the boost pump to catch any debris. Did you check it?

There’s an AD and SB for early Mooney’s up through the first 1000 or so Js with Dukes pumps to add this filter. It’s under the left exhaust cavity and hardly ever gets checked.

If the screens and injectors keep getting clogged, you might want to drain and inspect the tanks. The sealant is coming from somewhere. Also there is a really coarse screen on the tank outlet.

Skip

[EricJ]

+1 on verifying that there's an output screen on the fuel pump.    If there isn't one, it can be added per the AD/SB.   

Also +1 to check the hose between the servo and the flow divider.

Also, when removing the finger filter on the servo, remove it from the input hose side so that it doesn't trail crap back into the servo.

I've had those clogged injector issues before and they're no fun.

[jetdriven]

get a GATS jar and sump the full 12oz or whatever, a side before each flight. Perhaps it can remove some of the stuff.

 

[m100psi]

Thanks everyone for the suggestions.

I couldn't find the other thread on the fuel hose, but if it's the hose connecting the fuel servo to the divider, I'll just get that one replaced.

If there's a screen just after the boost pump, I don't think it was checked.  I'll look for it and ask my mechanic if the AD applies to my s/n if it isn't there.  My J is a '78.

I was under the impression that the screen on the servo was so fine, if crud was coming all the way back from the tank, it would either be filtered out there or too small to clog an injector.  Is that wrong?

Thanks,
Matt

[EricJ]

10 minutes ago, m100psi said:

I was under the impression that the screen on the servo was so fine, if crud was coming all the way back from the tank, it would either be filtered out there or too small to clog an injector.  Is that wrong?

Thanks,
Matt

That's how it's supposed to work, which is why the hose from the servo to the divider is always a suspect, and also why taking the servo finger filter out through the inlet helps, since it doesn't dump crap straight into the servo while being removed.

Since there are at least two other screens besides the servo screen for tank debris to get through (three if you have the post-pump filter) before getting to the injectors, debris from resealing is not the highest thing on the suspect list.

[adverseyaw]

What kind of particulate matter is clogging the injectors?

I had exactly this issue two years ago. Mine was silt in the tanks (possibly due to filling from oil drums? Just a guess). We had to pull apart most of the fuel system and clean it step-by-step. Sumping the tanks was NOT enough to find the silt -- it was only evident once the tanks were opened up and my mechanic got in there with a terry cloth.

If it's your boost pump or a hose coming apart, you may get lucky and can avoid complete disassembly. Based on the advice I got at the time, I suggest overhauling anything that comes into contact with the crud.

 

[Bartman]

I had this after installing a complete set of new fuel hoses.  The debris from either one of the new hoses itself or contamination on installation clogged the flow divider and was showering debris to multiple injectors too. I had multiple injectors with obvious debris and could not see thru them, but after cleaning them only to become clogged again. I ended up sending the flow divider off for service and the shop noted debris. No more problems after cleaning the flow divider. 

[FloridaMan]

Is it possible someone left the screen out of the fuel servo (Not sure if it can be reassembled without it)? Nothing should be getting through that. If the screen is there, I’d be looking for the source of contaminants between the servo and the injector. 
 

It looks like this and is where the hose connects on the port side of the fuel servo. 


 

to add: take a peak inside your tanks and make sure the fuel pickups still have their finger-shaped screens on them too. You can see them by looking inside the filler cap. 

Edited August 18, 2020 by FloridaMan

[carusoam]

A Florida Man has taken a nice pic of the screen!

Thanks for sharing that!

Best regards,

-a-

[adverseyaw]

The fuel servo finger screen has a spring-loaded override that will allow fuel and particulate matter past if it's sufficiently clogged. That's what was happening to mine.

(And yes -- great photo!)