So lost on this issue!

[JohnnyP]

76' 280z...I've been having a problem with lack of power/stumble/hesitation on acceleration. I've checked and adjusted; TPS, timing, vacuum advance, vacuum lines/hoses, clean spark to all plugs (new NGK's), new fuel pump (replaced for the sake of replacing it, not just to throw money at the problem!), flushed fuel lines, new fuel/oil filter, oil change, I checked and rechecked fuel pressure at the fuel rail…I real don't know what else to go through…

The car was running yesterday, I wake up this morning and try to start it..nothing! It cranks and sounds strong like it is JUST about to turn over, but it never gets that far. So I tried to crank it a few more times. On the third go, fuel starts spurting out of the #5 injector, right out of the top of the hose where the injector hose meets the fuel rail..Would I be correct in assuming that this means fuel is getting all the way to the injectors but isn't passing through? And this release of fuel through the hose is a symptom of a pressure build up in the fuel rail? Maybe a bad fuel injector pressure regulator? I'm confused on this one…Any help/suggestions/advice would really help me out! Thanks in advance to anyone.

John

[grantf]

have you tested you're fuel pressure after the filter? try that first. never mind reread youre post.........

Edited October 20, 2010 by grantf

[cygnusx1]

Is your cold start injector stuck open or closed? Does the spec fuel pressure remain in the rail for at least a few minutes after the car has been turned off? It should.

Distributor cap, rotor, and wires checked or changed?

Check the CTS, coolant temp sender and it's signal path back to the ECU for proper R vs Temp values.

System fuel pressure should never be able to exceed that which is specified in the manual, regardless of whether the injectors are firing or not. If spec pressure was exceeded for some reason, the fuel return circuit is suspect, including the FPR.

As the cold weather approaches, the injector hoses are notorious for leaking. Tighten them a bit.

Edited October 20, 2010 by cygnusx1

[JohnnyP]

Thanks for the advice. I forgot to mention that the wires, cap, and rotor were all changed out when I did the plugs, probably a few weeks ago. And they were checked recently as well.

I inspected the CTS, and it is connected as it should be. I am going to trace its signal path back to the ECU as suggested, next.

However, I did find that one of the connectors on the thermostat housing, with two wires (ground & bullet plug), where both wires are not attached to the actual part that is screwed in to the therm housing. The ground wire is grounded, and the bullet plug is plugged in, but neither are actually still physically connected to the that plug thats on the thermostat housing (broke loose from their solder). I don't know what this part is called exactly, its not the temp sensor or temp sender, that much I know. Could this be adding to the problem?

By the way, Cygnusx1…huge Rush fan!

[FastWoman]

A bad regulator won't cause your fuel hoses to blow/spurt. Your fuel pump will generate over 40 psi, but has an internal relief valve. In other words, if you completely block the fuel flow, your pressure will be a safe 45-ish psi.

[cygnusx1]

Rush are an amazing group of musicians. Can you take a photo of the sensors to help ID them? Also you need to make sure the temp sender for the ECU is giving you the proper resistance values. If it's out of spec, it could cause weird fuel mixtures and rough running for sure.

[grantf]

yes rush is amazing, Sorry off topic

[JohnnyP]

I've been searching a bit and can't figure out how to test that temp sender unit (check its signal path). Is there a specific test to run?

For a pic of the temperature switch that I mentioned is broken check the link! Post #4 is exactly the switch that broke on my thermo housing.

http://www.classiczcars.com/forums/showthread.php?t=35873&highlight=thermostat+housing

Thanks again all,

John

Edited October 21, 2010 by JohnnyP

[JohnnyP]

Is there a Haynes manual or E.F.I troubleshoot for the CTS?

[Zed Head]

A bad regulator won't cause your fuel hoses to blow/spurt. Your fuel pump will generate over 40 psi, but has an internal relief valve. In other words, if you completely block the fuel flow, your pressure will be a safe 45-ish psi.

I was in the FSM the other day for some reason, and realized that on Page EF-15, the description of the relief valve says "43 to 64 psi". I too was under the impression that the relief valve let go at 43 psi and have stated that several times myself in previous posts.

I'm not sure how I missed the 64 psi upper limit but it should be noted that 64 psi is a possibility. So it is possible to have a plugged line or regulator and get pressures considerably higher than 36 psi.

It would be interesting to pinch off the return line completely on a stock fuel pump and see where the relief valve lets go. Might not be safe though.

Edited October 21, 2010 by Zed Head

[FastWoman]

Zed Head, 64psi should still be safe. It's still not really that much pressure. I think these fuel lines are rated at something like 500 psi. Newer fuel injection systems run on much higher pressure too -- maybe up to 140 psi. Blocked injectors and bad fuel pressure regulators are often blamed for things like bulging fuel injector hoses and fuel rail leaks, but these things are more attributable to rotted rubber, corrosion, etc.

[cygnusx1]

Is there a Haynes manual or E.F.I troubleshoot for the CTS?

Absolutely! Download the original factory manual and it gives HIGHLY detailed step by step instructions and specifications. It also has a beautiful trouble shooting chart.

http://www.xenons30.com/reference.html

There are three sensors that I remember...coolant temp sender for the EFI, thermo-time switch for the ignition timing/cold start injector, and the sender for the temp gauge in the dash (the one that has the broken wire in your car). I am going to the manual now....

Edited October 22, 2010 by cygnusx1