#2 cylinder not firing 944S2
01-11-2019, 01:54 AM
#1
Racer
Thread Starter
#2 cylinder not firing 944S2
As the title says, I’m 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, there’s no fuel in cyl #2 even after running the engine.
I think there’s an issue with firing the injector, but I’m not sure what. How does the injector firing work? Does one of the injector leads get grounded to complete the circuit?
Thanks,
Camelman
I think there’s an issue with firing the injector, but I’m not sure what. How does the injector firing work? Does one of the injector leads get grounded to complete the circuit?
Thanks,
Camelman
01-11-2019, 03:57 AM
#2
Racer
Thread Starter
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
edit: corrected a typo to show 0V for the second lead
Last edited by camelman; 01-11-2019 at 11:57 AM.
01-11-2019, 07:05 AM
#3
Rennlist Member
Have you used a Noid light on #2? That will tell you if you're getting a signal to the injector.
01-11-2019, 07:18 AM
#4
Rennlist Member
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.
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.
01-11-2019, 11:56 AM
#5
Racer
Thread Starter
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 doesn’t sound right to me.
I have not checked the signal yet for #2 injector, but I did find 12V at each lead on the connector. That doesn’t sound right to me.
01-11-2019, 12:42 PM
#7
Rennlist Member
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 doesn’t sound right to me.
I have not checked the signal yet for #2 injector, but I did find 12V at each lead on the connector. That doesn’t sound right to me.
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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01-11-2019, 12:52 PM
#8
Rennlist Member
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
01-11-2019, 01:58 PM
#9
Racer
Thread Starter
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.
01-11-2019, 11:08 PM
#10
Racer
Thread Starter
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.
Can’t believe that didn’t come to mind first.
I listened to each injector with the engine running and they clearly tick. So, at least that system is okay.
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.
Can’t believe that didn’t come to mind first. I listened to each injector with the engine running and they clearly tick. So, at least that system is okay.
01-12-2019, 12:06 AM
#11
Racer
Thread Starter
I’m considering running trans fluid in the engine to see if it’ll clean out the hydraulic tappet and get it going again. If not, then I’ll swap in replacements. Thoughts?
01-12-2019, 08:58 AM
#13
Rennlist Member
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. Can’t believe that didn’t come to mind first.
I listened to each injector with the engine running and they clearly tick. So, at least that system is okay.
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.
Can’t believe that didn’t come to mind first.I listened to each injector with the engine running and they clearly tick. So, at least that system is okay.
01-12-2019, 09:34 AM
#14
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
01-12-2019, 11:46 PM
#15
Drifting
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.