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Meat Popsicle
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Discussion Starter #1
Had a dyno session this morning. First three pulls were normal, everything looked good on the datalogs. Fourth pull, the engine bucks around 4500-5000RPM so the shop owner shuts the engine off. We smell fuel but don't see a fuel leak so I ask him to prime the pump to check the pressure.

He primes the pump several times (I only wanted it primed once but whatever) and then I start to notice fuel leaking from the throttle body/intake filter. We pull the plugs, notice 3 and 4 are full of fuel.

Fast forward to me towing the car home, I pull the intake tube off and notice fuel accumulated in the supercharger S-tube. Yeah, it was THAT much fuel that it flooded the supercharger and the S tube completely.

So, the shop owner's theory is that one of the DSM injectors got stuck open. He mentioned that he's heard of that happening before. I suspect that when he primed the pump, the wide open injector flooded the intake manifold, supercharger, and S-tube.


I guess my first question is has anyone heard of this happening with DSM injectors before? These were cleaned and flowed by injector rehab and probably have less than 500 miles on them.

Secondly, is there any way that I can test if the injector is stuck open without spraying fuel through it?

I want to make sure that this is a mechanical issue and not something related to turboedit.

Thanks in advance,

Patrick
 

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got an extra injector pigtail and a 9volt battery? tap the injector on and off rapidly. have a finger on the injector and feel for it doing something
 

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Meat Popsicle
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Discussion Starter #4
Tried the 9v test and they all click...

So I’m no closer to figuring out why the hell the cylinders filled up with fuel.

I’m guessing one got stuck momentarily. I can’t see any other logical explanation for enough fuel flow to fill the cylinders and flow out of the throttle body.

When we were priming the pump to check fuel pressure, that’s when the fuel started coming out of the intake manifold.

Obviously the ECU has power in the 2nd ignition position (since it primes the pump) but it shouldn’t be sending a signal to the injectors right?


If that’s the case, I imagine I can disconnect the main relay, turn it to the 2nd ignition position and check for voltage at the injector plugs?
 

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Brokedick Millionaire
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40,228 Posts
In the worse wiring ever EF, then one I cut the ECU out because of 4-5 people trying to convert DPFI to MPFI to DOHC ZC there was an issue where if you put your foot on the brake, all injectors would hold wide open. Cycle the key/fuel pump a few times and the motor was filled was gasoline.

No rods were harmed because I "heard" the starter "grunt" and yell shut it off, I knew it was hydro locked on petro.
 

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Meat Popsicle
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Discussion Starter #6
Sounds like a nightmare bone.

I don’t think we hydrolocked the engine since the mass fuel quantities only started after shop owner primed the pump repeatedly.

Also, I’m fairly certain wiring isn’t an issue here since I procured one if the last available new OEM wiring harnesses several years back and there have been no modifications to it or the chassis harness (that I’m aware of).

My main concern here is ruling out turboedit as the cause.

The injectors shouldn’t have voltage when the pump is primed right?
 

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Brokedick Millionaire
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I've no clue on tuning and injectors with voltages...

Bu when you've heard a Walbro 255 HP dead head....and then it doesn't due to an open injector or two...pull the plugs and and pump it down like Top Fuel.
 

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if it dumped fuel when priming, unplug your injectors, unbolt the fuel rail, and lift off motor with injectors still in rail.

prime the car after finding a suitable container to sit rail and injectors over.

maYbe you have an injector that blew off the cap, a constant leak regardless of how good it clicks on and off.
 

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Meat Popsicle
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Discussion Starter #9
So I tried some low tech stuff this morning. First, I blew as hard as I could through the injectors and confirmed that none of them were open. Then I applied the 9v signal while also blowing through the injectors to confirm that they were opening and closing correctly.

I noticed that 1,3, and 4 would let a consistent stream of air through but there was definitely reduced flow through number 2.

If I had to guess, I’d say number 2 was the likely culprit.

Later, I’ll try to rig up the compressor to get 40psi to the injectors.

Either way, I’m going to replace the injectors with IN 600’s and hope for the best.

Thanks for the input guys
 

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Meat Popsicle
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Discussion Starter #10
LAMER made a good point via PM to check that the diaphragm on the FPR isn’t torn which would allow fuel to flow through the vacuum line into the manifold.

Will put vacuum on the FPR when I get home to double check that it’s not torn
 

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easy check is to prime the fuel pump several times with the vac line disconnected. Happens on Gm v6's from the 90s and early 2000s all too frequently
 

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if it does end up being a regulator, I believe i have my old reg from the d16y7 intake manifold if you want to make it work. and fuel rail, if the mounting is different.
 

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Meat Popsicle
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Discussion Starter #13
The FPR holds -20 in.Hg just fine so it’s not that.

Thanks for the FPR offer. I have to use a D16A1 regulator to fit the supercharger manifold which is something I should also replace since my current one is god knows how old.

I wrote Joe to see if he’s heard of any versions of TE holding an injector open. I’m doubting that this was the case but I’ll see what he says.

Thanks again for your replies Matt
 

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Have to installed noid lights at the injectors to verify the ecu is pulsing the ground path?

Pulled the ecu lid to check for any leaking caps? Or burnt tracks or diodes?
 

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Meat Popsicle
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Discussion Starter #15
Have to installed noid lights at the injectors to verify the ecu is pulsing the ground path?

Pulled the ecu lid to check for any leaking caps? Or burnt tracks or diodes?
Not yet. I've checked the injectors by putting 40psi of air pressure behind them and using a 9v battery. They all open/close just fine and weren't sticking when I tested them.

I planned on disconnecting the injector plugs and testing for voltage at the plug before I removed the injectors but I couldn't afford to risk flooding the cylinders again if one was stuck open.

If I can disconnect the fuel pump from the access cover, I'll pull power to it, put the key in the run position, and see if there's voltage at the injectors.
 

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Meat Popsicle
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Discussion Starter #16 (Edited)
Should the injector plugs show 12v when the engine isn’t running and the key is in the run position? I’m seeing 12v on all of them but the injectors are closed.

Edit: followed the FSM troubleshooting procedure which says the ECU is bad.

Wish I hadn’t sold the Zdyne now so I could swap it in and recheck

Any chance that one if you with an OBD0 or OBD1 vehicle can unplug one of your injectors, turn the key to the run position (without cranking) and see if you have 12v on the 2p injector plug?
 

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There should be 12v with the ignition on, the ground signal is generated from the ECU

The flow chart in the FSM is for diagnosing a fault code. If you don't have a fault code then you can't definitely come to a conclusion with that flow chart. It does help to diagnose problems with components though. Ie: checking the resistance of the injectors.

Another thing to check would be that the injector wiring isn't grounding out somewhere other than the ECU. If you unplug the ECU, test continuity to ground at the injector plug. Red/blk is power, the other wire should be your ground signal (changes colour per injector). There should be no continuity.
 

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Meat Popsicle
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Discussion Starter #18 (Edited)
There should be 12v with the ignition on, the ground signal is generated from the ECU

Another thing to check would be that the injector wiring isn't grounding out somewhere other than the ECU. If you unplug the ECU, test continuity to ground at the injector plug. Red/blk is power, the other wire should be your ground signal (changes colour per injector). There should be no continuity.

Engine NOT running, key in the RUN position...

There should be 12v to the injector red/blk wire. I should be able to read 12v if I test between red/blk and a body ground.

But, I wouldn't think that I should be seeing 12v between the red/blk and the corresponding ground wire on the 2P injector connector.

All the red/blk wires are hot with the ignition in the RUN position but the ECU shouldn't be providing a ground if the engine isn't running.


Or am I way off on this?


Another thing to check would be that the injector wiring isn't grounding out somewhere other than the ECU. If you unplug the ECU, test continuity to ground at the injector plug. Red/blk is power, the other wire should be your ground signal (changes colour per injector). There should be no continuity.
Tested this, per the FSM, and there is no 12v signal via the two wires in the 2P injector connector once I disconnect the 17P connector from the ECU.
 

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Engine NOT running, key in the RUN position...

There should be 12v to the injector red/blk wire. I should be able to read 12v if I test between red/blk and a body ground.

But, I wouldn't think that I should be seeing 12v between the red/blk and the corresponding ground wire on the 2P injector connector.

All the red/blk wires are hot with the ignition in the RUN position but the ECU shouldn't be providing a ground if the engine isn't running.


Or am I way off on this?
You're not way off, that's all correct.

Tested this, per the FSM, and there is no 12v signal via the two wires in the 2P injector connector once I disconnect the 17P connector from the ECU.
So it's sounding like either an unfortunate intermittent injector failure, or an unfortunate intermittent ECU problem. Did you say that it was a couple of injectors that were stuck open? If so, it seems more likely to be the ECU...
 

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B-series Destroyer
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912 Posts
I'm surprised I didn't see this thread. I used to have DSM injectors in my car. Last year at the track, on my second lap, I had my car start running like crap. AFR's were extremely rich. Throttle off was still showing 16.0 AFR's. I'm sure that is what happened to me. I had an extra set of injectors with me that day, I swapped out to the original injectors and it ran fine for the rest of the weekend.
 
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