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#2 cylinder not firing 944S2

Old 01-11-2019, 02:54 AM
  #1  
camelman
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Default #2 cylinder not firing 944S2

As the title says, Iím down a cylinder. Compression shows 180psi on cyl #2, the #2 plug fires fine with a strong spark, I cleaned all injectors and all four spray well (I even swapped injectors between cylinders), and I see 12V on each lead for the #2&3 injectors. However, thereís no fuel in cyl #2 even after running the engine.

I think thereís an issue with firing the injector, but Iím not sure what. How does the injector firing work? Does one of the injector leads get grounded to complete the circuit?

Thanks,
Camelman
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Old 01-11-2019, 04:57 AM
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I just read that one terminal on each injector plug should be at 12V with ignition on and engine not running with the other terminal at 0V. Sounds like I have a short somewhere?

edit: corrected a typo to show 0V for the second lead

Last edited by camelman; 01-11-2019 at 12:57 PM.
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Old 01-11-2019, 08:05 AM
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Otto Mechanic
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Originally Posted by camelman View Post
I just read that one terminal on each injector plug should be at 12V with ignition on and engine not running with the other terminal at 9V. Sounds like I have a short somewhere?

Have you used a Noid light on #2? That will tell you if you're getting a signal to the injector.
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Old 01-11-2019, 08:18 AM
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Post Script:

If you find the injector is getting a signal from the harness, remove it and test it using a nine volt battery. If it clicks audibly, it's responding to the signal and it may be blocked by gunk, in which case you should remove all the injectors and send them out for cleaning and matching (Witchhunter seems the most popular service provider for this). If it doesn't, you probably have a failed injector.
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Old 01-11-2019, 12:56 PM
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I removed and cleaned the injectors using a 12V source to trigger the injectors. They seemed to work just fine. When I reinstalled them I switched the #1 injector to the #2 location, but #2 continues to be the problem. It seems the no-fire issue is not related to the injector.

I have not checked the signal yet for #2 injector, but I did find 12V at each lead on the connector. That doesnít sound right to me.
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Old 01-11-2019, 01:27 PM
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Sounds like you might have a damaged valve issue. I recommend a compression check next.
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Old 01-11-2019, 01:42 PM
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Originally Posted by camelman View Post
I removed and cleaned the injectors using a 12V source to trigger the injectors. They seemed to work just fine. When I reinstalled them I switched the #1 injector to the #2 location, but #2 continues to be the problem. It seems the no-fire issue is not related to the injector.

I have not checked the signal yet for #2 injector, but I did find 12V at each lead on the connector. That doesnít sound right to me.
There is 12V to both leads when the engine is not running. The DME pulses one lead to ground when starting and running of the engine. Check resistance of each lead to #2 cylinder injector by removing the DME Connector from the DME. Use an ohm meter and a wire lead from the engine bay to each of two pins separately in the connector for #2 cylinder to measure the wire resistance of each injector lead.
I believe ohm reading should be 0.4 ohms or less.

Check Clark Garage for more details on specific pins in the DME connector for #2 cylinder. Although the electrical dwg, see Pelican Parts, shows the injectors pulsing in pairs, the reality is all 4 injectors pulse simultaneously.
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Old 01-11-2019, 01:52 PM
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Originally Posted by mytrplseven View Post
Sounds like you might have a damaged valve issue. I recommend a compression check next.
OP did a compression test and #2 cylinder was 180 psig. As mytrplseven stated it could be a valve issue eventhough the compression valve was OK. There could be a failed valve spring on the intake valve which impedes the closing of the valve on the compression stroke. Do a leak down test of #2 cylinder and other one for comparison
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Old 01-11-2019, 02:58 PM
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T&T, thanks fo the guidance on the injector triggering and testing process. Since I'm not getting any fuel residue in the #2 cylinder (even with the engine running on the other three cylinders), I'm going to start with the injector harness. I'll run a leak down test this weekend too.
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Old 01-12-2019, 12:08 AM
  #10  
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I checked CR again and got the following:
1: 190psi
2: 130psi
3: 190psi
4: 190psi

I had a noisy lifter in the #2 cylinder a while back that had to be pumped up to work sometimes. I think that might actually be the culprit. Canít believe that didnít come to mind first.

I listened to each injector with the engine running and they clearly tick. So, at least that system is okay.
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Old 01-12-2019, 01:06 AM
  #11  
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Iím considering running trans fluid in the engine to see if itíll clean out the hydraulic tappet and get it going again. If not, then Iíll swap in replacements. Thoughts?
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Old 01-12-2019, 09:50 AM
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Originally Posted by camelman View Post
Iím considering running trans fluid in the engine to see if itíll clean out the hydraulic tappet and get it going again. If not, then Iíll swap in replacements. Thoughts?
Opinions on adding ATF the motor oil are as varied as what brand motor oil is best. Here's what Amsoil writes about it: Amsoil


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Old 01-12-2019, 09:58 AM
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Originally Posted by camelman View Post
I checked CR again and got the following:
1: 190psi
2: 130psi
3: 190psi
4: 190psi

I had a noisy lifter in the #2 cylinder a while back that had to be pumped up to work sometimes. I think that might actually be the culprit. Canít believe that didnít come to mind first.

I listened to each injector with the engine running and they clearly tick. So, at least that system is okay.
I believe the hydraulic lifter has failed. If it was call, I would replace the failed one and not try the ATF route
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Old 01-12-2019, 10:34 AM
  #14  
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Could be the Ballast resistor by the left hand strut, it has 4 resistors feeding the 4 injectors, remove the plug and meter it out, you should have 5 wires, the red is the supply, and the resistance should be 6 Ohms to the other 4 wires
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Old 01-13-2019, 12:46 AM
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I have a question. When you started the post you said the #2 cylinder was 180 psi. The latest compression showed it at 130. What has changed? Was the lifter on cylinder #2 making a knocking noise when you noticed this problem? Usually when I've had a faulty lifter, it was very noisy. If it wasn't making a lot of noise, then I'm wondering if it might be a bad valve or something else in the cylinder like a bad ring, cylinder head gasket, bad seal around spark plug, etc.
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