Sarah's 1991 Camaro

saleen 192

Core Member
you playing with the 6 CYLINDER MOTOR TODAY ?
 

TransAmDan

Forum Admin
Staff member
you playing with the 6 CYLINDER MOTOR TODAY ?
I plan to, but then I was hoping to yesterday. Took the day off work and the day just vanished, took the TA out for a run, done a bit of programming.
A friend popping around this morning, and walking aunties dogs this afternoon.
I do plan on checking the positive side of the injectors, perhaps even make something to make the injector operate.
 

TransAmDan

Forum Admin
Staff member
Found an injector I can actually unplug and get to.
IMG_20201017_140502.jpg

So rigging up the scope to check. Looking at thus with a volt meter I can see 12V, but dies it hold while cranking? A scope would be a better tool for this test.
IMG_20201017_140841.jpg

Right hand side should be ignition live through a fuse. The left side is switched ground from the ECU.
Would be hard to monitor this with it plugged in to the injector, however this is the same wires that go to the other two injectors on this bank. So I should see some good pulses at this point.
 

TransAmDan

Forum Admin
Staff member
1602940709049.png
Well this shows something interesting. Under 8V across the injector.
As I am measuring across the injector plus this can be two things, the 12V is dropping out, or not a perfect 0V to the ECU.

Next is to find what is dropping out.
 

TransAmDan

Forum Admin
Staff member
Between alternator ground and the positive feed to the injectors. Not as low as the previous waveform.

We can see a good 12v when not cranking then when cranking we see around 10V on the injectors when they are not firing, and down to 8V when they are trying to.
1602941222009.png
 

TransAmDan

Forum Admin
Staff member
So below, I have taken the scope direct to the battery, so this is bypassing all the wiring and fuses, a known good 12V. Only just exceeding 8V, so this is better, but not perfect, so this is telling me it is not pulling 0V very good, which suggest the bad ground. This is why the pump wasn't working due to bad ground. I know I visited grounds before, tested many and around 0.2ohms or less. I think it is now worth removing some grounds, clean them up and reapply them. The ECU has 3 ground connections, but don't know where they all are on the body, one is rear of the passenger side heads.
1602941569027.png

Another good investigation, I feel I'm getting closer. Do injectors let through any fuel at all at 8V? I'm guessing its like a relay coil, a 12V relay starts humming below 10V.

Got to pop out again, but I may do a bit more tonight or maybe tomorrow evening.
 

saleen 192

Core Member
Found your problem you last this car will start now lol
 

Attachments

  • Screenshot_20201017_203842_com.android.chrome.jpg
    Screenshot_20201017_203842_com.android.chrome.jpg
    452.4 KB · Views: 0

Will

Core Member
Dan, I'm sure it's a silly question at this point, but presumably the battery has enough balls to crank the thing and run the fuel injection without the voltage dropping off too much?
I know it's a completely different animal, but that Jeep Grand Cherokee I had simply refused to start one winter despite seeming to crank fast enough. Turns out the battery was weak! I fitted a brand new one and it burst into life.
 

TransAmDan

Forum Admin
Staff member
Dan, I'm sure it's a silly question at this point, but presumably the battery has enough balls to crank the thing and run the fuel injection without the voltage dropping off too much?
I know it's a completely different animal, but that Jeep Grand Cherokee I had simply refused to start one winter despite seeming to crank fast enough. Turns out the battery was weak! I fitted a brand new one and it burst into life.
Good question. Battery is a couple of years old, brought it to get the Camaro going. Its been kept in good condition, spent most of the time sitting under the stairs. Since it's been in the engine bay only the negative is left connected. Have my battery conditioning charger on it too. It seems to turning pretty quick. I do have the TA next to it, so I can jump from that for done extra oomph.
Just finishing up some work, then I'll go to play with earth's.
 

Will

Core Member
Good question. Battery is a couple of years old, brought it to get the Camaro going. Its been kept in good condition, spent most of the time sitting under the stairs. Since it's been in the engine bay only the negative is left connected. Have my battery conditioning charger on it too. It seems to turning pretty quick. I do have the TA next to it, so I can jump from that for done extra oomph.
Just finishing up some work, then I'll go to play with earth's
Ah, OK. It's probably not the battery then, but I guess a jump start from a healthy and running car would rule that out.
For checking the earths, I'd go for temporarily grounding them out with a direct feed to the battery negative to eliminate those.
 

TransAmDan

Forum Admin
Staff member
Ah, OK. It's probably not the battery then, but I guess a jump start from a healthy and running car would rule that out.
For checking the earths, I'd go for temporarily grounding them out with a direct feed to the battery negative to eliminate those.
Good idea, can use a jump lead to create an earth point. Should finish up work in 10mins, then I'll pop out there for a play.
 

TransAmDan

Forum Admin
Staff member
Got to an earth stud on the back of the block, 3 ring crimps on it, which was 4 wires and a strap. Cleaned up and reassembled. It was a pain to get to, had to remove the low voltage wires to the dizzy to gain access and still was tight.
Tried to start, still no go. Jump leaded with 50mm2 cables from a 1000amp battery with the TA running, enough power to light up Frankensteins monster. Rev counter showed the starter was spinning it at 1000rpm. Still no luck.
However there is an earth on the other head looks rusty, may get better access from underneath. A few other earth I can see that need some attention.
Maybe more time available tomorrow to have more of a play.
 

TransAmDan

Forum Admin
Staff member
Have you pulled an injector and tested it yet?
Nope, nothing to test it with. Wouldn't be able to rig up a fluid flow test without buying something. Can't easily remove the fuel rail with injectors to test that way as they are hard fuel lines, and nothing to hold injectors in so fuel would leak everywhere.
I do have an electrical tester, gave it 12v across the injector, no noise, but think the tester couldn't deliver enough current, so needing to retest that with a fused live. Ohms on the injector looks normal for an injector.
My next plan it so see how far away the ECU earth is from chassis earth while cranking. If there is a difference I'll create a new earth for the 3 earths on the ECU.
 

AmericanThunder

Super Moderator
Just pull the injector, place the end in a bottle and apply ground. It should fire visibly and safely. If the hard lines don’t allow it, ground an injector for a cylinder that’s on the intake stroke (inlet valve open) and remove that plug. Place something absorbent in the plug hole and see if it gets fueled.
Also, July92 mentioned that the oil pressure sender needs to be operational for the injectors to fire and I will second that. Also tested?
 

TransAmDan

Forum Admin
Staff member
Just pull the injector, place the end in a bottle and apply ground. It should fire visibly and safely. If the hard lines don’t allow it, ground an injector for a cylinder that’s on the intake stroke (inlet valve open) and remove that plug. Place something absorbent in the plug hole and see if it gets fueled.
Also, July92 mentioned that the oil pressure sender needs to be operational for the injectors to fire and I will second that. Also tested?
If I pull the injector it can't fire anything as no fuel can be connected to it.
The oil pressure sender dosn't appear to be causing any issues. There is 12V on the injector, the other side is pulled to ground from the ECU which isn't reaching true ground, its about 4 volts off, indicating a bad earth somewhere.Still searching for that earth, which is why my next step is to check the ECU earth while cranking. As earth are saying zero ohms, but this is when there is no load, pretty sure there is a rotton one when pulling current.
 
Top