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Vacuum leak around rear secondary injector, stumped
I recently went through my FD and replaced the injector o rings, diffusers, grommets/insulators, PD, FPR, lines, etc. All replacement parts are OEM. Car has simplified sequential set up with new vacuum lines and emissions equipment removed. Trying to diagnose a high idle problem, I found a vacuum leak around the rear secondary injector that I can't get to seal up.
With the car started, I used a water bottle with a hole poked in the lid to squirt water around under the intake until the car bogged down and I heard a hissing noise. Noise comes from in front of the FPR. I did this multiple times to ensure if was from there. Note there is no fuel smell.
OMP lines and injectors and crush washers are new. I don't think the primary injectors would be the culprit. Plastic spacer under primary rail is installed. I was careful to grease all of the rubber parts when I installed them, too.
I replaced the FPR vac line, no change. Re-sealed the block off plates in that area, no change. I pulled the secondary rail back off and made sure the grommets were present. Pulled the diffusers out and made sure their o rings weren't pinched. I even replaced the new grommets with another new pair, no change.
Going off of this, I installed everything as pictured so I don't think I forgot anything.
Anyone have any suggestions? Could the secondary rail not be fully seated?
My suggestion is if you want to test your work on the fuel system then put a fuel pressure gauge on the FPR and run the car. Note the pressure. Shut off the car and see how fast the pressure drops. If you see the pressure drop back down to zero you probably have a leak in the fuel system some where. I've seen a healthy fuel system hold pressure for hours and sometimes a very long time. If you see it quickly drop back to zero it's leaking. Then you have the chore of finding where.
Seems it's sucking in air by a gasket and not a fuel leak. If the fuel system was leaking you would smell it and likely see it if fuel system was to open air like that.
What you need is a smoke test. Inside the garage with car running and no wind around put some smoke around the area to see where it's pulling into the motor.
I'd suggest, the nipple on the LIM that points to the rear and connects to the fpr solenoid might have been overlooked.....easy to do, being virtually out of sight - and mostly inaccessible!
Are you sure this is not the deliberate "vacuum leak" shown as the very dark blue line(s) in these vacuum line diagrams? The line taps the intake tube of the forward turbo and runs to the two primary injector air mixing tubes below the injectors. This hose is at ambient pressure.
I questioned this connection in a previous post, but it was explained to me that the purpose was to improve evaporation of incoming fuel. But I've never heard any sound from it on our '94. Just a thought... you might want to test it by pulling off that hose from the turbo inlet pipe and plugging it temporarily, to see if the sound goes away.
(My high-idle problem was due to the original fiberboard gasket between the LIM and the rotor housing having burned through and leaking; I fixed it by replacing the gasket with the later stainless-steel part from Mazda.)
Are you sure this is not the deliberate "vacuum leak" shown as the very dark blue line(s) in these vacuum line diagrams? The line taps the intake tube of the forward turbo and runs to the two primary injector air mixing tubes below the injectors. This hose is at ambient pressure.
I questioned this connection in a previous post, but it was explained to me that the purpose was to improve evaporation of incoming fuel. But I've never heard any sound from it on our '94. Just a thought... you might want to test it by pulling off that hose from the turbo inlet pipe and plugging it temporarily, to see if the sound goes away.
(My high-idle problem was due to the original fiberboard gasket between the LIM and the rotor housing having burned through and leaking; I fixed it by replacing the gasket with the later stainless-steel part from Mazda.)
Are you sure the dark blue lines aren't to the OMP injectors. And the yellow line is the injector mixing port connected to the Y-pipe?
Originally Posted by grimple1
Here's one for a single turbo conversion:
Nevermind the red circle.
Last edited by ondabirdhouse; 11-20-15 at 05:50 PM.
My suggestion is if you want to test your work on the fuel system then put a fuel pressure gauge on the FPR and run the car. Note the pressure. Shut off the car and see how fast the pressure drops. If you see the pressure drop back down to zero you probably have a leak in the fuel system some where. I've seen a healthy fuel system hold pressure for hours and sometimes a very long time. If you see it quickly drop back to zero it's leaking. Then you have the chore of finding where.
Seems it's sucking in air by a gasket and not a fuel leak. If the fuel system was leaking you would smell it and likely see it if fuel system was to open air like that.
What you need is a smoke test. Inside the garage with car running and no wind around put some smoke around the area to see where it's pulling into the motor.
Exactly, I'm not getting any fuel smells at idle/driving/under boost either (I was prior to the fuel system overhaul). I'm going to look into that smoke test, I have never heard of it. Thank you.
Originally Posted by billyboy
I'd suggest, the nipple on the LIM that points to the rear and connects to the fpr solenoid might have been overlooked.....easy to do, being virtually out of sight - and mostly inaccessible!
Thank you- I actually replaced that one with a new vac hose and zip tied the ends (a bitch with the fuel rails installed too!). Didn't change anything though.
Originally Posted by wstrohm
Are you sure this is not the deliberate "vacuum leak" shown as the very dark blue line(s) in these vacuum line diagrams? The line taps the intake tube of the forward turbo and runs to the two primary injector air mixing tubes below the injectors. This hose is at ambient pressure.
I questioned this connection in a previous post, but it was explained to me that the purpose was to improve evaporation of incoming fuel. But I've never heard any sound from it on our '94. Just a thought... you might want to test it by pulling off that hose from the turbo inlet pipe and plugging it temporarily, to see if the sound goes away.
(My high-idle problem was due to the original fiberboard gasket between the LIM and the rotor housing having burned through and leaking; I fixed it by replacing the gasket with the later stainless-steel part from Mazda.)
I did route the OMP air intake lines to the front turbo inlet pipe. I replaced the fuel atomizer line from the Y pipe too. I'll double check both of those though. Thanks.
You bring up a good point with the LIM to block gasket, I thought about it too.
Tomorrow I am going to try some sort of smoke test. I might also try to make a water squirter with a nozzle or something so I can better direct the water around the intake.
OK, I read through this again and one thing I can't figure out is what are the SYMPTOMS that you have a vacuum leak?
Typically a post-throttle body vacuum leak will result in a higher than normal idle and enough of one will make the car run weird.
You can't go by sound, there's lots of weird sounds in the engine bay.
If I'm working on a car with a high idle (actually just worked on one with a high idle), first I look for an obvious vacuum leak - hose not connected, vacuum cap leaking or missing, etc. Then, I spray starting fluid around in short bursts on suspected areas. The engine will rev up and smooth out when it sucks in the starting fluid.
Past that, a throttle cable adjusted too tight or the throttle body not shutting completely due to misadjusted throttle stops is the next thing to look at. Then, clean and lube the ISC, a sticking ISC can cause weirdness.
I'm at a loss understanding (in both your post and the OP's) the reference to OMP air lines. The OMP (Oil Metering Pump) lines carry oil, not air, and do not appear in the vacuum hose diagrams.
There are vacuum lines that go to the top of the oil injectors. Those attach to the rat's nest and end up going to one of the nipples that is on the primary turbo inlet. Basically it's just a source of filtered air.
Many people just vent to atmosphere or put little mini filters on them.
There are vacuum lines that go to the top of the oil injectors. Those attach to the rat's nest and end up going to one of the nipples that is on the primary turbo inlet. Basically it's just a source of filtered air.
Dale, I have been under the impression that those lines have nothing to do with oil injection, but rather aid in atomizing the fuel. Is that wrong?
OK, I read through this again and one thing I can't figure out is what are the SYMPTOMS that you have a vacuum leak?
Typically a post-throttle body vacuum leak will result in a higher than normal idle and enough of one will make the car run weird.
You can't go by sound, there's lots of weird sounds in the engine bay.
If I'm working on a car with a high idle (actually just worked on one with a high idle), first I look for an obvious vacuum leak - hose not connected, vacuum cap leaking or missing, etc. Then, I spray starting fluid around in short bursts on suspected areas. The engine will rev up and smooth out when it sucks in the starting fluid.
Past that, a throttle cable adjusted too tight or the throttle body not shutting completely due to misadjusted throttle stops is the next thing to look at. Then, clean and lube the ISC, a sticking ISC can cause weirdness.
Dale
Symptoms are a high idle around 2000-2500 RPMs. Car drives fine, just a handful to drive slow like through a parking lot or neighborhood.
I've double checked the tightness of the throttle and cruise cables, played with the butterfly stops to see if a turn in or out made the idle drop, double checked my vacuum hoses/your check valves, and re-sealed all of my block off plates. I have the ACV and AWS removed and blocked off. Simplified sequential setup also.
After that didn't change anything, I started spraying around the engine with a water bottle and found that the engine bogged down when I sprayed water around the secondary fuel rail. So the intake came back off, I checked all the lines again, replaced the FPR to LIM vac line and, replaced the secondary injector grommets with another new pair. Started the car and problem still remains.
So I'm confident it's a vacuum leak around the secondary fuel rail, I'm just stumped at what it could be since I've replaced everything around there.
I'm wondering if it may be the LIM to block gasket as wstrohm mentioned. My reasoning is that I used a lot of carb cleaner and a rags when I had the rats nest off cleaning up the engine (brittle wiring harness wrap pieces, old vac hose, grime). I wonder if that could have caused the ancient stock gasket to bite the dust.
Not sure if it matters, but my PFC shows an injector duty of 8/9 % when the car is idling. I understand why it might read this with the post-TB vacuum leak, just wanted to mention it if it might matter.
Originally Posted by wstrohm
Dale, I have been under the impression that those lines have nothing to do with oil injection, but rather aid in atomizing the fuel. Is that wrong?
I believe the yellow line here going from the downward pointing nipple on the Y pipe and is the fuel atomizer line. And then you have the dark blue lines with the air feed to the OMP injectors.
Last edited by BrettLinton7; 11-22-15 at 10:17 PM.
Had a lim to block multi-layer metal gasket leak, evident with fuel leaking down the block, but that was through lots of re-use....sounds like that isn't the case here?
I couldn't identify a defect comparing it to a new replacement either - did fix the issue though - I probably would have sprayed it with hylomar if time wasn't an issue.
Had a lim to block multi-layer metal gasket leak, evident with fuel leaking down the block, but that was through lots of re-use....sounds like that isn't the case here?
I did have a fuel leak prior to replacing everything, that's a good thought.
I tinkered with the car more and I'm leaning more towards the LIM to block gasket- when I turned the engine off, I poured about a cup of water under the intake, wanting to rinse off and dilute all the carb cleaner I had been spraying under the intake.
When I went to start the car a minute later, it took substantially longer and once fired up, it sputtered and choked for a few seconds. I would think that if the water puddled up against the LIM and block, it would have sucked that into the engine and that would have caused the hesitation to start.
Would that make sense? Anyone have any ideas how I could check that gasket besides pulling everything off and replacing it? I'd imaging the turbos have to come off for that, yipee...
I'm at a loss understanding (in both your post and the OP's) the reference to OMP air lines. The OMP (Oil Metering Pump) lines carry oil, not air, and do not appear in the vacuum hose diagrams.
The dark blue line --
Originally Posted by gsl-se addict
The purpose of the lines, as I understand it, is
1. To better atomize the oil
2. To equalize pressure as you and T.J. have already mentioned
As you said, the pressure is lower (higher vacuum) at the base of the injector than at the other end of the vacuum line, so the air flows into the oil injector. In addition there is a check valve in the top of each injector that only allows air to flow in that direction. The oil is pumped into the center of the injector via the OMP, while the air flow from the vacuum line pulls the oil into the engine and breaks the oil up into finer droplets in the process.
If you didn't have the lines the vacuum would pul the oil up the OMP lines, as T.J. said. With the check vavle and the air line, as vacuum is generated, air is allowed to enter through the top of the injector, eliminating the vacuum draw on the OMP lines. It could just as well have the vacuum lines removed with atmospheric pressure on the other side. But Mazda chose the route becuase the area before the throttle plates, which is basically at atmosphric pressure, but the air has been passed through the air filter, so it is clean.
Kent
The yellow line next to the oil injectors/blue lines is the fuel injector mixing atomization port which is connected to the Y-pipe.
Originally Posted by gsl-se addict View Post
The purpose of the lines, as I understand it, is
1. To better atomize the oil
2. To equalize pressure as you and T.J. have already mentioned
As you said, the pressure is lower (higher vacuum) at the base of the injector than at the other end of the vacuum line, so the air flows into the oil injector. In addition there is a check valve in the top of each injector that only allows air to flow in that direction. The oil is pumped into the center of the injector via the OMP, while the air flow from the vacuum line pulls the oil into the engine and breaks the oil up into finer droplets in the process.
If you didn't have the lines the vacuum would pul the oil up the OMP lines, as T.J. said. With the check vavle and the air line, as vacuum is generated, air is allowed to enter through the top of the injector, eliminating the vacuum draw on the OMP lines. It could just as well have the vacuum lines removed with atmospheric pressure on the other side. But Mazda chose the route becuase the area before the throttle plates, which is basically at atmosphric pressure, but the air has been passed through the air filter, so it is clean.
Kent
The yellow line next to the oil injectors/blue lines is the fuel injector mixing atomization port which is connected to the Y-pipe.
OK, now I'm really confused. But thanks much for the link to the "Injector Atomization Pipe" thread, it did help me. The yellow line in the diagram comes from the Y-pipe, which is at the output of the turbos, which pressure will vary from atmospheric all the way up to 10+ psi. Its destination appears to be a single port near the primary injector, but it is not shown or mentioned in the "Assembly" section of the 1994 Workshop manual. The dark blue lines in my link go to the tops of the OMP injectors. Those lines originate at the input of the forward turbo and carry filtered air at atmospheric pressure (no boost and no vacuum).
If the "yellow line" follows boost, thus keeping its air pressure the same as the intake manifold pressure, why don't the lines to the OMP injector also follow intake manifold pressure? If the rotor chamber is under boost and the OMP air is not, isn't that a "boost leak" back through to the input of the turbo? And why doesn't the manual show the fuel atomization air connection at the rotor housing?
Pressure at the y pipe is higher under boost than the intake manifold. Also the diffusion is much more important at low rpm where air flow velocity is low.
The blue lines to the OMP injectors see filtered air because they draw in air when the rotor chamber has vacuum. An internal check valve in the OMP injector prevents positive rotor chamber pressure (boost) from spitting the injected oil back out through the top. The purpose for leaving the top of the injector open, is so that the negative air pressure (vacuum) does not drink or suck the oil from the OMP. The oil is more...drooled, into the chamber. This is why it is important that the check valves in the injectors are operational or else lubrication under boost could be non existent.
@OP
Hopefully your vacuum leak is not the LIM gasket. You need to remove the turbos to change the gasket. As mentioned, a smoke test could be helpful here.
Hopefully your vacuum leak is not the LIM gasket. You need to remove the turbos to change the gasket. As mentioned, a smoke test could be helpful here.
Thanks, Matt, for the explanation in your post above. But regarding your quote above, I'm not the OP and have no vacuum leak (since replacing the lower LIM gasket a couple of years ago). I'm just an innocent bystander...
@OP
Hopefully your vacuum leak is not the LIM gasket. You need to remove the turbos to change the gasket. As mentioned, a smoke test could be helpful here.
Matt
Originally Posted by 7krayziboi
Cigar upside down in pop bottle works too
Thank you both. I'm going to try the smoke test with the complete intake on, but I think it will be hard to track down the leak if it's under the intake. If I can confirm that it's after the UIM but can't direct it down, I'm going to remove the UIM and make a plate to seal up the top of the LIM, then give it another whirl. Probably won't get around to it until this weekend.
Smoke test showed it was the LIM to block gasket. Quite a leak too! New gasket will be here soon, probably won't have it installed until after Christmas.
I put rubber gloves over the exhaust and intake pipes to seal that up. Then I pulled off a line to the UIM and put my smoke tester line on. Blew and found smoke coming from under the UIM. So I pulled the UIM off and made a quick cardboard cover to go over the LIM ports. Poked a hole for the smoke test vac line and repeated the procedure. The video below shows the obvious leak.
I took a few pictures of my smoke tester if anyone was interested. I did it at midnight after I couldn't sleep, it's not fancy but it got the job done.
Sealed off the intake pipes and exhaust:
Here is the tester. A cigarette is in the short, fat line. Blow in the long line going into the side of the bottle and smoke comes out the short line coming from the top.
Thankfully grandma left her cheap cigarettes here a while back.
Testing it once the UIM was off.
She's all buttoned up for now...
Last edited by BrettLinton7; 12-02-15 at 04:24 PM.
thanks for sharing your test method. I'm like you, i can't sleep if i have an issue with the car and want to troubleshoot it. I've worked on my stupid car early in the am, late at night and in freezing cold weather.
Have fun replacing the gasket. When i got my car i also had a leak there.
thanks for sharing your test method. I'm like you, i can't sleep if i have an issue with the car and want to troubleshoot it. I've worked on my stupid car early in the am, late at night and in freezing cold weather.
Have fun replacing the gasket. When i got my car i also had a leak there.
Thanks. I'm fortunate enough to have a heated garage (basement) so it's easy to wander down there. Beats working on it in parking lots like I did in my FC days.
I'm glad I found out the problem, just wish it wasn't such a bitch to replace.
11-20-15 | 12:17 PM
