Lost and need help.1993 ZR1

[Route 66]

I have a problem with my 93 ZR1. I have not been able to get the 405 HP for some time. I haven't had the time to work on it again tell now. I started trying to find why I don't have the 405 about 6 to 8 years ago. Thought then it was because of vacuum leaks under the plenum. Pulled plenum and repaired all the leaks. Checked actuators they seamed to work like they should. Installed new vacuum solenoid. I put it back together it did not solve the problem. So I left it tell about a week ago and started once more to find the problem. Checked fuel pressure will not go higher than about 43lbs psi at 3000 RPM. After shutting the engine off the pressure will drop to about 15 psi in about 1 hour. Replaced fuel filter. Also while I had the fuel lines open I thought I would check the Y hose connection in the tank. Pulled the Fuel pump. I had put a new GM ZR1 fuel pump assembly in when I worked on it the last time.[6 to 8 years ago] It still looked as new as when I put it in the tank. I don't think it would be leaking pressure there. All hoses and fittings looked good
One more thing I am not getting any Check Engine trouble codes. I get the 12 code. I was getting a service LTPWS. I solved that problem. Plus I don't think there is a connection between the 2. Now no Codes and no 405 HP.
Your help would would be most appreciated Thanks Ellis

Took this picture today of the pump I installed back then. I am not sure but I do not think this is my problem.

[jss06c6]

Does your vacuum pump cycle on and off fairly frequently? 43 psi is a bit low in the fuel pressure for sure. Have you changed out the fuel filter? I'm assuming you are reading the fuel pressure off the end of the fuel rail on the passenger side? You might try installing a long hose to the fuel rail with a pressure gauge that you can bring into the cab or tape it to the dash and then take the car out for WOT run. Get a passenger to record the fuel pressure for you.

Do you have a performance chip in the car? If so, whose chip is it (Haibeck, etc)?

Is the valet key still operational?

Need some more info to help you chase this down.

Sent from my XT1585 using ZR-1 Net Registry mobile app

[Paul Workman]

Originally Posted by Route 66

I have a problem with my 93 ZR1. I have not been able to get the 405 HP for some time. I haven't had the time to work on it again tell now. I started trying to find why I don't have the 405 about 6 to 8 years ago. Thought then it was because of vacuum leaks under the plenum. Pulled plenum and repaired all the leaks. Checked actuators they seamed to work like they should. Installed new vacuum solenoid. I put it back together it did not solve the problem. So I left it tell about a week ago and started once more to find the problem. Checked fuel pressure will not go higher than about 43lbs psi at 3000 RPM. After shutting the engine off the pressure will drop to about 15 psi in about 1 hour. Replaced fuel filter. Also while I had the fuel lines open I thought I would check the Y hose connection in the tank. Pulled the Fuel pump. I had put a new GM ZR1 fuel pump assembly in when I worked on it the last time.[6 to 8 years ago] It still looked as new as when I put it in the tank. I don't think it would be leaking pressure there. All hoses and fittings looked good
One more thing I am not getting any Check Engine trouble codes. I get the 12 code. I was getting a service LTPWS. I solved that problem. Plus I don't think there is a connection between the 2. Now no Codes and no 405 HP.
Your help would would be most appreciated Thanks Ellis

NOTE: Edited for clarification...

Several things are left undone, far as troubleshooting goes:

When you say "no 405 horsepower" are you referring to no FULL ENGINE POWER on the DIC screen on the dash?

When you turn the ignition switch on, does the vacuum pump run for a few seconds and then shut off for at least 5-10 seconds before restarting? Or does the pump run continuously?

Are you certain the secondary actuators are operational? Marc Haibeck's web site has a procedure for verifying the secondary actuators are (in fact) operating. (Cliff too has this procedure in his SOLUTIONS section.)

What is the fuel pressure at WOT? Typically it should be 53-55 psi (see photo of setup (below). W/o the secondaries running, the dynamic fuel pressure is in the 43-45 range. Deviations from these parameters usually indicate fuel delivery issues, i.e., pump(s), fuel lines, fuel filters, pressure regulator, regulator vacuum hose disconnected - that sort of thing.

Does your snorkel (accordion hose) between the filter box and the air horn collapse at WOT? If your snorkel does NOT have Marc Haibeck's wire hoops installed on the inside of the hose, OR there is no metal sleeve inserted internally in the hose, then it may well be the (stock) accordion snorkel hose is collapsing: UNLESS, there is one of the Samco hoses replacing the accordion style hose, then collapsing is not the issue. Otherwise...it COULD BE!

Connecting a VOM (configured to measure AMPERES) is inserted between the battery POSITIVE post and the fuel pump diagnostic connector (on the big wire loom, a red wire with a black plastic connector, jutting out near the wiper motor). You should measure 4-5 amperes for each pump, or 8-10 TOTAL if both are operational. (Test with the ignition switch OFF).

Let us know what you find and we can go from there.

[QB93Z]

Paul just asked all my questions while I was typing.


Jim

[Ccmano]

[Bob Eyres]

I had a similar low pressure problem on my 91’.
It also exhibited a long cranking, slow start condition.
The pumps had been replaced in the past, but fresh fuel pumps cured the condition immediately.
Please post your results. Driving the car must feel like going for a hike with lead boots on.


Sent from my iPhone using ZR-1 Net Registry

[Route 66]

Originally Posted by Bob Eyres

I had a similar low pressure problem on my 91’.
It also exhibited a long cranking, slow start condition.
The pumps had been replaced in the past, but fresh fuel pumps cured the condition immediately.
Please post your results. Driving the car must feel like going for a hike with lead boots on.


Sent from my iPhone using ZR-1 Net Registry

Thank You and the others who have responded to my request for help. I have the pumps out at this time. Trying to do what I can to keep the assembly from rusting like the one that came with the car when new. Been looking for all stainless steel hose clamps. The made in china clamps are not all stainless an might rust!! Grainger has stainless clamps made in USA that are 100 percent stainless. If any one is thinking of replacing the hose clamps inside there gas tank....5/16 to 5/8 Part #1A527. 10 pack less than $10. total

I will be trying some of the things you and the others have suggested when I get the pump back in.



I will keep you and the others posted..Thanks again Ellis

[Route 66]

Originally Posted by Paul Workman

NOTE: Edited for clarification...

Several things are left undone, far as troubleshooting goes:

When you say "no 405 horsepower" are you referring to no FULL ENGINE POWER on the DIC screen on the dash?

When you turn the ignition switch on, does the vacuum pump run for a few seconds and then shut off for at least 5-10 seconds before restarting? Or does the pump run continuously?

Are you certain the secondary actuators are operational? Marc Haibeck's web site has a procedure for verifying the secondary actuators are (in fact) operating. (Cliff too has this procedure in his SOLUTIONS section.)

What is the fuel pressure at WOT? Typically it should be 53-55 psi (see photo of setup (below). W/o the secondaries running, the dynamic fuel pressure is in the 43-45 range. Deviations from these parameters usually indicate fuel delivery issues, i.e., pump(s), fuel lines, fuel filters, pressure regulator, regulator vacuum hose disconnected - that sort of thing.

Does your snorkel (accordion hose) between the filter box and the air horn collapse at WOT? If your snorkel does NOT have Marc Haibeck's wire hoops installed on the inside of the hose, OR there is no metal sleeve inserted internally in the hose, then it may well be the (stock) accordion snorkel hose is collapsing: UNLESS, there is one of the Samco hoses replacing the accordion style hose, then collapsing is not the issue. Otherwise...it COULD BE!

Connecting a VOM (configured to measure AMPERES) is inserted between the battery POSITIVE post and the fuel pump diagnostic connector (on the big wire loom, a red wire with a black plastic connector, jutting out near the wiper motor). You should measure 4-5 amperes for each pump, or 8-10 TOTAL if both are operational. (Test with the ignition switch OFF).

Let us know what you find and we can go from there.

Thanks for responding.. You asked about the DIC showing a FULL ENGINE POWER. It doesn't show one when power key is turned on or off. Engine running or not running. I get the green light on at the power key when it is on.
It has been a long time since I have gotten the 405 HP to work I don't remember seeing a FULL ENGINE POWER on the DIC.
I did turn the ignition on to see if the DIC displayed a FULL ENGINE POWER it did not show it with ignition on but not running.

I will try again in a couple of days after I get the fuel pump back in.
About the actuators had them opening and closing with a mighty vac before I sat the plenum back on when I repaired the vacuum leaks. The secondary vacuum pump works as it should it is new.

I appreciate you help I will respond to your other questions when I get the pump back in and engine started. Thanks again Ellis

[secondchance]

93 does not display full engine power on DIC. Green light next to the power key only.

[Paul Workman]

Originally Posted by secondchance

93 does not display full engine power on DIC. Green light next to the power key only.

Roger that. Green light by the key.