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2G Leaking boost in middle of FIC injector??

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ScrubyMcBubble

Probationary Member
18
7
Apr 25, 2013
Winnipeg, MB_Canada
Hello everyone! I need your guidance and opinions. Swear ive googled to the moon an back on this one and found nothing here or there.

I'm boost testing my 95 GST and found that my FIC 1200 Hi-Z's are leaking in the middle. Not on the seats or the fuel rail but right in the middle close to where the wires connect. Short videos attached for the TL;DR
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To explain further i start by turning the key for the fuel pump to kick in and pressurize the rail, pinch the vacuum line for the MBPR, pump 20 - 25 psi of pressure from my air compressor into the turbo inlet. Spray everything down with soapy water and found no notable leaks except for bubbles from all 4 of my injectors in similar places, and also from the OEM Fuel pressure regulator.

When supplying FIC with the videos they were very quick to send me another set under warranty (Awesome support from this vendor!). After installing the new set they have near identical symptoms however the leaks are slower and more subtle. The previous owner has stated it has a walbro 255 fuel pump (certainly whines like one) but it only has the OEM Fuel pressure regulator so im thinking my next steps should be to get a FuelLab or Aeromotive AFPR and new lines.

Something about this still doesnt seem right to me and i still can't explain why i have these symptoms. If air can leak from the injectors, would fuel not leak from them too (especially at 43.5psi)?? Could this be caused from a failed diaphragm in the oem FPR?

More car context: It came tuned on a piggyback SAFCII with 550's, i have since swapped for 1200 FIC Hi-Z's with ECMlink and added a fresh wideband. I went as far as tuning idle on speed density before taking a step back to make sure there wasn't anything missing that could cause me to have to tune it all over again.. So im looking at the basics first before proceeding with anymore tuning. I saw no signs of fuel leaks and smell no gas when i was tuning idle.

Only had this one for 2 years so its a work in progress.
 
Weird - First time seeing this. So what do you think is happening? Is air pushing around the nozzle of the injector, up into the injector body? It must not be pushing air into the fuel rail?

Closed injectors will hold back the fuel, and not let the air into the fuel rail.

Under operating conditions, I'd expect some kind of vacuum leak, and on boost some kind of a boosted air + fuel mix pushing through the injector body.

Maybe small - but there it is - you can see it well with the soap bubbles.
 
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What i think.. I have hunches but nothing concrete enough to press on without looking for a second opinion. I know I should have an AFPR when using a walbro 255 so I was hoping there's something I just don't understand about the oem FPR that could cause this LOL. Probably not so simple.. i can deal with a leak at the rail or the seat but the spot these injectors are leaking seems like a manufacturer defect since it's leaking from between the injector body and the blue height adapter. What throws me off is that the warranty replacements have the same symptoms with only slightly more subtle leaks. Maybe I'm just unlucky twice?

That's a good point you make regarding vacuume leak. I've not had the car under boost at any point since the injectors were installed so that may be why I never noticed gas smell or leaking. I only had it tuned to for 14.7 afr idle in the driveway since installing them.

I'm guessing just a bad seal between the injector and height adapters.
I'll have to get in touch with the vendor again but I wanted to confirm with the community here to make sure it wasn't something else causing it.
 
What i think.. I have hunches but nothing concrete enough to press on without looking for a second opinion. I know I should have an AFPR when using a walbro 255 so I was hoping there's something I just don't understand about the oem FPR that could cause this LOL. Probably not so simple.. i can deal with a leak at the rail or the seat but the spot these injectors are leaking seems like a manufacturer defect since it's leaking from between the injector body and the blue height adapter. What throws me off is that the warranty replacements have the same symptoms with only slightly more subtle leaks. Maybe I'm just unlucky twice?

That's a good point you make regarding vacuume leak. I've not had the car under boost at any point since the injectors were installed so that may be why I never noticed gas smell or leaking. I only had it tuned to for 14.7 afr idle in the driveway since installing them.

I'm guessing just a bad seal between the injector and height adapters.
I'll have to get in touch with the vendor again but I wanted to confirm with the community here to make sure it wasn't something else causing it.
I doubt the fpr is related in any way to this leak.

I run stock FPR with a 260lph Supra Green, similar to the 255. I would not spend on a FPR unless you have an over/under pressure issue.
 
I doubt the fpr is related in any way to this leak.

I run stock FPR with a 260lph Supra Green, similar to the 255. I would not spend on a FPR unless you have an over/under pressure issue.
Had a thought, I'm not very confident in the readings on the gage on my fuel filter. Perhaps my fuel pressure is dropping lower than my air pressure during the test? I'm thinking it might be a more accurate test to jump my fuel pump relay so it's active. Then I can pump air pressure and the fuel pressure should compensate accordingly correct? This way I can see if I'd leak fuel under boost, or if the bubbles keep going.

Thoughts? Is it safe to jump the fuel pump to keep it running for this test while the car is off?
 
Had a thought, I'm not very confident in the readings on the gage on my fuel filter. Perhaps my fuel pressure is dropping lower than my air pressure during the test? I'm thinking it might be a more accurate test to jump my fuel pump relay so it's active. Then I can pump air pressure and the fuel pressure should compensate accordingly correct? This way I can see if I'd leak fuel under boost, or if the bubbles keep going.

Thoughts? Is it safe to jump the fuel pump to keep it running for this test while the car is off?
yes, you can turn the pump on and it won’t cause an issue. The return line to the tank is flowing while the pump is running, and it should hold base fuel pressure + whatever air pressure you add to the manifold.
 
yes, you can turn the pump on and it won’t cause an issue. The return line to the tank is flowing while the pump is running, and it should hold base fuel pressure + whatever air pressure you add to the manifold.
I jumped the fuel pump using the fuel pump test wire on the firewall and tested again. Super strange, I smell no fuel and see no fuel leaks after having the fuel pump run for a while. My fuel pressure regulator is working and compensating for pressure im adding to the intake. Did the soap test again and... still air bubbles LOL
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I'm hesitant to send back my injectors just yet as this is the second set (warranty replacement) currently on the car. The warranty replacement ones look a little more like refurbs (minor scratches and blemishes). I sent this to FIC to see if they can make sense of what's happening.
 
yes, you can turn the pump on and it won’t cause an issue. The return line to the tank is flowing while the pump is running, and it should hold base fuel pressure + whatever air pressure you add to the manifold.

I jumped the fuel pump using the fuel pump test wire on the firewall and tested again. Super strange, I smell no fuel and see no fuel leaks after having the fuel pump run for a while. My fuel pressure regulator is working and compensating for pressure im adding to the intake. Did the soap test again and... still air bubbles LOL
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I'm hesitant to send back my injectors just yet as this is the second set (warranty replacement) currently on the car. The warranty replacement ones look a little more like refurbs (minor scratches and blemishes). I sent this to FIC to see if they can make sense of what's happening.

You have established that there is no fuel leaking when the injectors are closed, and the FP is providing pressure, and the FPR is increasing the fuel pressure as the intake manifold pressure increases. - You still have air pushing past the tip seals of the injector nozzle.

If the engine were running - the injectors would open - spraying fuel into the intake runner. Some part of that pressurized air/fuel would presumably leak back up through the seals - same as a static test with only air. Small - yes. important? hard to say.

Good call talking to FIC to see what to do next.

-j
 
Those injectors seem to have some sort of cup they sit in for DSM use. I suspect the sealing of the injector Insulators to the head and what ever seal between the injector and the cup.

The fuel rail looks pretty corroded, is the mating area in the head clean and smooth so the injectors can seal?
 
Those injectors seem to have some sort of cup they sit in for DSM use. I suspect the sealing of the injector Insulators to the head and what ever seal between the injector and the cup.

The fuel rail looks pretty corroded, is the mating area in the head clean and smooth so the injectors can seal?
I'll pull them again tonight and try polishing the area with a scotch pad or something to be sure. A lot of the corroded look on my fuel rail and intake is the soapy water having dried to it. I haven't rinsed or wiped it away yet and it's leaving a crusty white corroded look to the aluminum when dried.
 
My 2150 FIC's are like Steve described. They have special "hats" that have a oring to seal them also inside the hats if I remember correctly as one set I got had the wrong "hats" on them (the were for a Suburu or some other import, but the injector was the same, only the "hat" was different).
Maybe yours has an issue in that area.
Sorry I couldn't see the videos on my Government computer. :banghead:
 
I cleaned up the area where the injectors sit on the head, and cleaned where they connect to the rail. All the o-rings and seats look good with no wear or scratches. I've always lubed them with engine oil before installing.

The bubbles still persist slowly from 10psi or higher intake pressure. I had my fuel pump running during this test to ensure fuel pressure was high enough to compensate for air pressure.

I asked a mechanic at a local shop and they figured it wasn't an issue and that the conditions I'm putting on the setup are not likely to occur naturally. They said that with a running engine air the system should be in vacuum pulling any air available rather than leaking from the injectors. Not sure how true this is, it's just one mechanics opinion.

I'm also wondering if it's possible that there are multiple layers to these injectors like a cosmetic outer shell that could let air slip between without pushing through the injector body. It seems unlikely that air is actually pushing through the injector body against a much higher fuel pressure unless there is a alternative route for the air to flow completely isolated from the fuel.

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Would something like this make sense? Red lines fuel, teal lines for air.

And if this was the case, is it an issue worth me stressing over?

Thanks for the valuable input as always!

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Have you taken the tops off of the injectors and looked inside to check the seal there? The top is a "cover" to mate to our rails and there was an oring INSIDE of that cover on my 2150s.
 
Marty, do you have an upper injector sheet, the buffer that fits between the rail and injector body that provides the downward pressure on the insulator to seal it?

ScrubyMcBubble, What we think is going on, air from your pressure test is leaking around the injector insulator in the head into the injector cup and up the body to leak out at the top of the cup. I don't see any way for the air pressure to go into the injector body to leak out from above the connector and the upper cup only around it.
 
I removed the injector height adapter cap (hat/cup) from one to have a look. The seal looks fine.
Wondering if perhaps the issue would be the cup/hat not being fully compressed to the top of the injector by the clamping force of the fuel rail? Seems unlikely to have the same issue with 8/8 identical injectors which pushes me to suspect the fuel rail or spacers for the fuel rail.

I'm in the middle of a fuel system overhaul at the moment including new Fuel Lab AFPR, FL filter, -6 AN fittings and PTFE lines. I picked up a new FIC fuel rail while I was at it to rule out possible rail issues.

Let me know if I'm on the right track or missing something, input is always welcome.

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Looking closer at the injectors height adapters and the seal for the top of the injector.. the seal doesn't get pressed between the hat/cup and tip of the injector. The tip of the injector protrudes past the seal so the only thing that could happen from additional mounting pressure is metal on metal contact with the cap/hat. So the seal is between the sidewalls of the cap/cup and the side of the injector tip.. if they are not sealing all I can think of is uneven seating of the cap/hat? Maybe the cap/hat sits a little crooked on top when mounted under my fuel rail?

Anyways.. I'll just go forward the the fuel system changes and hope for the best outcome LOL
 
Marty, do you have an upper injector sheet, the buffer that fits between the rail and injector body that provides the downward pressure on the insulator to seal it?

ScrubyMcBubble, What we think is going on, air from your pressure test is leaking around the injector insulator in the head into the injector cup and up the body to leak out at the top of the cup. I don't see any way for the air pressure to go into the injector body to leak out from above the connector and the upper cup only around it.
I run my injectors off a stock rail with stock hardware. Not sure what the "upper injector sheet" thing is. The 3 bolts that hold the rail onto the head is all the pressure that mine use and they don't leak @steve
I am still trying to figure how AIR can get into the fuel system, they are 2 seperate dedicated systems. The only way I see compressed air getting to the point we all see the bubbles is thru the injector needle. Please correct me if I am mistaken.
 
Not sure what the "upper injector sheet" thing is.

The injector sheet is the rubber filler that is wedged between the fuel rail and the injector body. By compressing it the fuel rail presses the injector into the insulator and seals it.

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Ok, I see. My 2150s don't use a sheet only the upper o-ring and the insulator. Thanks for the pictures.
Now you have me scratching my bald head. I am sure I don't use them but I do on the Low Z injectors. The Hi Z's I have don't have a place for the sheet if IRRC. Dam memory is getting as bad as my hearing.......
 
Something needs to act as a buffer/spring pushing the injector into the insulator or the injector body needs to be engineered to fit so the rail does so directly as things expand and contract.
 
Now I gotta open the hood :hmm: ..........I am sure it is just the rail and the proper spacing between it and the head.
 
I wouldn't be surprised if that's how your are. I guess I'm questioning the design here.

I assume there isn't any fuel leaking so the o-ring between the injector and the upper cup is fine but air is leaking up from the head and the lower adapter cup.
 
That is what I am puzzled about. The only place those two meet is at the tip of the injector, isn't it?
 
The 1200’s have a really long pintle. The big lower piece is just an adapter. It’s totally possible for the o rings to leak and allow air to escape from in between the adapter and injector body, like your videos.
 
The 1200’s have a really long pintle. The big lower piece is just an adapter. It’s totally possible for the o rings to leak and allow air to escape from in between the adapter and injector body, like your videos.

Ya, but how would it be making bubbles at the lip of the upper adapter cup?
 
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