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Discussion Starter #1
I have an intermittent problem that is strange. This is a SBF with 16 injectors, 8-30lb primary and 8-220lb secondaries. The large secondary injectors turn on around 3.5 lb boost while on the transbrake.

The problem is this - put the car on the transbrake, go full throttle and the rpms/boost comes up very predictable. Just in the last few weeks it started having an problem. Once the secondary injectors kick in the engine runs rough and doesn't have full power. Fortunately I have EGTs in each cylinder so I could see #7 cylinder temperatures were dropping off quickly so I knew what cylinder causing the problem. It was fine last week at the track but last night it started happening again.

I changed the plug and plug wires and that made no difference so I eliminated that as a possibility. I decided to make a pass just to see how it acted going down track and #7 dropped off on the transbrake as it does when the problem is happening and then going down track the EGTs on the datalogger showed me that #7 cylinder would power up then drop off, come back then drop off again. So it was even intermittent going down the track.

Since it only happens on boost with the secondary injectors firing, it's apparently related to the secondary injectors. So earlier today I switched #7 and #8 secondary injectors and wiring. I warmed the car up and put it on the transbrake 6-7 times and each time it acted normal - full power and no problem with either cylinder EGT falling off. I was hoping the problem would occur and I could either identify or eliminate the #7 injector/wire/ECU driver as the problem.

I was wondering if anyone had an injector or injector driver go bad and act this way. The injectors are Siemen Deka and are 8 years old.
 

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Discussion Starter #3
Maybe it was just a loose connector and now that you swapped them it’s ok?
I doubt it. The connector was clipped on solidly. However, I can't rule out the wire in the harness yet.
 

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Discussion Starter #5

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On the trans brake, then off and on going down the track....hmmmm
Maybe investigate the 2 step ? If you use the the older style chip in the 2 step module, sometimes the chip fails .
 

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Discussion Starter #7
On the trans brake, then off and on going down the track....hmmmm
Maybe investigate the 2 step ? If you use the the older style chip in the 2 step module, sometimes the chip fails .
No 2 step is used on the transbrake. Only rev limiter is the Haltech 2500 rev limiter set at 7000rpm. It has a rev limiter that could be used on the TB but I normally don't use it.
 

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Are you running Ign1a coils Randy? Sounds like it's load related to me which would lean me more toward spark. If you have a spare coil, I would swap that one out. Have you moved the injector to another cylinder to see if the issue follows?

Frank
 

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Discussion Starter #10
Are you running Ign1a coils Randy? Sounds like it's load related to me which would lean me more toward spark. If you have a spare coil, I would swap that one out. Have you moved the injector to another cylinder to see if the issue follows?

Frank
Yes I have the 1A coils and yes, I've already moved the injector but the problem hasn't shown up since then.

The coil is next on the "list" once it occurs if it doesn't follow the new location for the injector and stays with cylinder 7. The reason I'm focusing on the secondary injector right now is because when it does occur it happens immediately when those injectors "kick in" and that is only at 4lbs boost. Last week it went down the track at 18lbs boost clean as can be. But the week before that run while in the driveway it was dropping the cylinder on the TB.

But I do have a spare coil, it's just a little more difficult than usual to replace because the coils are in the plenum the cowling. They all come out as an "assembly" so it takes a while to change one coil. It's a nice place for them away from the heat and there's not a good spot in the engine compartment for them.

99972
 

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Discussion Starter #11
compression test
That will be the last "test". There are no indications of a bad cylinder driving and the problem is either on or off. Once I clear the injector/injector driver and wire harness I'll change the coil to test that also. If none of those clear the problem then I will do a combined compression/leakdown test.
 

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Discussion Starter #13
you can drive around all day and make low boost on a bad hg and not know
Not if you have individual EGTs. A bad cylinder sticks out like a sore thumb even during cruise.

Even without the individual EGTs, the problem is either there or not. A bad cylinder would not be intermittent.
 

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Discussion Starter #14
Well the mystery is partial solved. The car ran fine at the track last night up to 22lbs boost. However, while sitting in the staging lanes waiting I was looking hard at the ECU for anything I had missed. At the bottom of the display there is a little obscure item called "DTC" which, when opened up, shows faults the ECU has perviously detected. I rarely look at this since most are faults that naturally occur. I opened the display and It showed 3 faults and one of them showed exactly what I suspected - a problem with #7 secondary injector circuit.

Now I just need to figure out if it's the injector or the wiring though I strongly suspect it's the wiring since the harness is an old OEM injector harness that has been modified.

100109
 

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Yes I have the 1A coils and yes, I've already moved the injector but the problem hasn't shown up since then.

The coil is next on the "list" once it occurs if it doesn't follow the new location for the injector and stays with cylinder 7. The reason I'm focusing on the secondary injector right now is because when it does occur it happens immediately when those injectors "kick in" and that is only at 4lbs boost. Last week it went down the track at 18lbs boost clean as can be. But the week before that run while in the driveway it was dropping the cylinder on the TB.

But I do have a spare coil, it's just a little more difficult than usual to replace because the coils are in the plenum the cowling. They all come out as an "assembly" so it takes a while to change one coil. It's a nice place for them away from the heat and there's not a good spot in the engine compartment for them.

View attachment 99972
Man you have a lot of engineering done under that hood. Nice work!
 

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Maybe ask Haltech if the current monitoring is before or after the injector driver.
My spidey sense tells me it's monitoring the injector current draw and the injector is going south. (It is this way in a lot of UCM/ICMs I use at work.)
Maybe ohm the suspect injector along with a good one both cold and after being heated up with heat gun or hot blow dryer; one probe on a pin, the other clamped to metal on the injector nozzle, then maybe on both pins.
It surprised me one time when I had an injector issue and when I ohm checked it in the engine I had continuity to the head. I've always heard about it but never found the "shorted coil" until that one.
 

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Discussion Starter #17
Man you have a lot of engineering done under that hood. Nice work!
Yep, there's a lot of stuff going on under the hood on this car. When I first got the coils I couldn't figure out where to put them, there simply is no "nice" spot under the hood. After pondering it for a day or so, I started thinking "why not inside the cowl area". It's a great spot for them but trust me when I say they JUST fit and there was one area of the floor section that had a to be pounded down with a hammer to make room for the furthest one to the left. One of the windshield wiper mechanism arms had to be sectioned and a new piece welded in to clear the coils.
 

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Discussion Starter #18
Maybe ask Haltech if the current monitoring is before or after the injector driver.
My spidey sense tells me it's monitoring the injector current draw and the injector is going south. (It is this way in a lot of UCM/ICMs I use at work.)
Maybe ohm the suspect injector along with a good one both cold and after being heated up with heat gun or hot blow dryer; one probe on a pin, the other clamped to metal on the injector nozzle, then maybe on both pins.
It surprised me one time when I had an injector issue and when I ohm checked it in the engine I had continuity to the head. I've always heard about it but never found the "shorted coil" until that one.
I'm confident it is monitoring the circuit downstream of the injector driver which essentially is the lead the ECU uses to ground the injector since they all share the same +12V power.

It could be the injector but i doubt it. I've already checked it's coil resistance and compared to a few others (2.2 ohm) and it was the same. If it was a failure to high temperature as you suggested, it probably would have shown itself last night at the track. The outside air temperature was 90+ degrees and the engine water temperature stayed between 170 and 200 deg F during all three runs.

I suspect it's in the wiring and when I relocated the injectors and their wires, I had to adjust the wiring harness and that "fixed it" though I'm not doing to rely on this for long term. I have to find some new injector connectors that will fit my setup. The Ford OEM connectors are slender and just fit. The typical "new" aftermarket connectors are all fat with a spring wire to release the clip. I bought one of those and figured I might be able to fit the fat ones, but it will take some effort to get them to clear in the tight area they are.

100251
 

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I'm confident it is monitoring the circuit downstream of the injector driver which essentially is the lead the ECU uses to ground the injector since they all share the same +12V power.

It could be the injector but i doubt it. I've already checked it's coil resistance and compared to a few others (2.2 ohm) and it was the same. If it was a failure to high temperature as you suggested, it probably would have shown itself last night at the track. The outside air temperature was 90+ degrees and the engine water temperature stayed between 170 and 200 deg F during all three runs.

I suspect it's in the wiring and when I relocated the injectors and their wires, I had to adjust the wiring harness and that "fixed it" though I'm not doing to rely on this for long term. I have to find some new injector connectors that will fit my setup. The Ford OEM connectors are slender and just fit. The typical "new" aftermarket connectors are all fat with a spring wire to release the clip. I bought one of those and figured I might be able to fit the fat ones, but it will take some effort to get them to clear in the tight area they are.

View attachment 100251
crimp the pins onto wires then epoxy them into the injector and remote the connector where you have room.

Crap solution...but a solution for a tight space.
 
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