Compression Question

[pablo_max]

All, Thanks again for the help so far.

I tested the compression this week and found that all the cylinders are around 170.However, this number is not reached until the 4th compression cycle. It starts out at around 110 or so and then jumps up in each remaining stroke until the maximum compression of 170 is reached. Is this normal? I was thinking perhaps this tells me there is something wrong with the rings. This car has been sitting for more then 1 year without being started, so it is for sure possible there was crap stuck all over the rings and the valves. A older fella I work with told me that when they got motors that sat for a long time, they would drain the oil and put a gallon or so a gas in the the crank case, disconnect the ignition so it cant fire, and then turn it over for 15 seconds or so and that would clean out all that old stuff and normally restore the seal to the compression rings. Has anyone heard of that?Is it worth trying that before I take off the head?

Thanks a lot.

Patrick

[evildky]

taking time to build the pressure is kinda normal, what weight oil is in the car? is it new oil? or old oil? thin or old oil can take more time to build a seal and leakout more quickly, honestly I wouldn't worry about the compression at this time if you got good consistant readings

as for the gas thing, I'd always heard diesel fuel, which would be safer as it's higher octane, the problem with this kind of plan is that if it dislodges a bunch of gunk, where will it lodge itself next? I'd concentrate on finding the real problem, if you got good consistant compression then your problem has to do with fuel or spark

[pablo_max]

Well, the thing is though, the car has no power what so ever. i mean to get to 60 I am pretty sure I would have to be driving down hill.

I had an electrical problem with the ECU to where the car would not run at all, but after messing around with it, I got it running. I dont think it would be an engine management problem, do you?The fuel filter is new. The injectors are new. Fuel lines are new. I didnt change the pressure regulator, but I would imagine it's either working or I would not have a running at all. The timing is set right. The plugs, wires and cap are new. vacuum advance seems to be doing its thing. PCV was replaced. Dont see any vacuum leaks. I am fresh out of ideas actually.

[sharjt]

If all that is working and you rev and nothing happens it's probably your Clutch.

[evildky]

is the car running on all 6 cylinders? injector connectors are a commin problem, they harden and crack and stop working, you might be running on 4 or 5 cylinders

[pablo_max]

Do you know of an easy way to check that the connectors are working?I know these guys use a square wave, so I am rather hoping I dont need to use an o-scope. A multi-meter is for sure not fast enough so see if its working..it would imagine is should be firing that guy 3-4 times per second.

[pablo_max]

Ok.. here is the latest.

I took your advice to check that the injectors were even firing..I used a stethoscope to listen first on the back three and heard nice click click click but there was nothing at all going on with the first three. So I used a volt meter on the plugs to see if there was any voltage at all. Zero on the first three and .3 or so on the backs. Now just for further poops and giggles, I took off the 1st three plug wires, not really any difference at all. There is a slight difference because even with no fuel it would still burn the EDR gases. Now, when i take off any 1 of the back 3, it just about dies right away. So, I cant say with 100% certainty that it is the ECU, but I can imagine what else it would be. I did take that sucker out and there was some water damage on it. I could see that some of the components were basically shorted out because of all the crap on there. I may try and replace the damaged parts, but I think they will be hard to locate. I dont have a wire diagram for the ecu, so I dont know which pins control the front 3 injectors...anyone know that???I was thinking I should just jumper on to the connector assembly in the ECU to see if the pulses are coming at all. Does anyone know any other reason at all that the front three injectors would not get the pulse before I drop 200.00 on the new ECU?? Please guys, I need some advice on this one.Thanks a lot.Patrick

[evildky]

glad we're now on the right path, see I know it couldn't be that beautiful indestructable L6

it could also be a bad harness, all the injectors get their power from the single fuel injector relay, (can't remember if thats the one under the dash or behind the battery, but either way it's green and controls all 6) might also try finding a used ECU to try, or someone was talking a while back abotu a place that rebuilds ECU's heck they are local to me but I can't remember the name to save my life, might want to search a bit

[pablo_max]

Yes, I will for sure look at that relay too. I would however need to find out if that relay is getting the pulse from the ECU to send the power to the injectors no? Is that relay under the hood or under the dash? I didnt take any notice of it before.Its actually surprising how much power is still has as a 3 banger

I found on a parts site the diagram of the inside of the relay and it appears to be broken into two parts, so it may well be that the relay is not switching on the 2nd channel. Time to bust out the o-scope.

[evildky]

if you have power to half the injectors then the relay should be working, but the path is broken, taht would point to a bad harness, you might want to unwrap the narness and look for any shorts, I believe the fuel injector relay is the one on the passanger side behind the battery facing into the hold in the inner fender hehind the battery, just follow the injection harness you'll find it but it powers all 6 so I still say check the harness

[NissanSportMag(Z31)]

Power for the injectors comes directly from the ECU. There are two triggers inside it. Each trigger operates 3 injectors.

[pablo_max]

Here is an update..I found that the trigger was not getting to the relay and not leaving the ECU, so I got a new ECU and it worked. Now the car runs like a top Thanks for the help..Now I just need to replace the shocks, brakes, rack and pinion and she's done

Thanks again for all the help!