failure to start after warmed up - ZR-1 Net Registry Forums

orthodoct · 04-09-2017

Gentlemen:
Brand new problem. Car running fine after rebuild. Had my hair cut yesterday and got 92 ZR1 up to operating temp. Got back in car to go home about 30 minutes later. Starts, runs 3 or 4 seconds and dies. Throttle appears unresponsive at that time. Started about ten times then had to be towed home, seventy five bucks wasted! Once cooled down to below about 150 degrees oil temp, started just fine. Suspected fuel problem, but even with problem, Schrader valve on fuel rail is pressurized. Ran diagnostics this AM and no codes are set. Neither FP1 or FP2 fuses open. Fuel pump/sender unit is new and got it from Jerry about a year or so ago. Fuel filter changed when new pump assembly installed. Started this AM and ran up to operating temp of 192. Restarted immediately, but when attempted to restart ten minutes later, once again starts and runs 3-4 seconds and dies. No evidence of fuel starvation at WOT when running. I read about potential problem with loss of primary fuel pump and fact that both primary and secondary pumps run on startup (until 176 degrees I think that I read??) and then secondary shuts down except when secondary injectors come on line. If primary pump dead, would expect fuel starvation at WOT and it is a new unit. 92 ZR1 owned since new, Haibeck chip, new injectors from Jerry, rebuilt everything under plenum, new clutch from Bill Boudreaux, Stainless Works headers with Corsa exhaust. Has run flawlessly for over a year until this happened. What to do???
Thanks!
Ty (orthodoct)

Jagdpanzer · 04-09-2017

Sounds like the same problem I had right after acquiring my 94 ZR-1 ten years ago. Turned out to be the primary fuel pump had seized up. When first starting cold the ECM runs both fuel pumps until 176 degree F coolant temperature is reached. Then it cuts back to just the primary fuel pump. If the primary fuel pump is not working the engine will immediately shut down due to lack of fuel pressure. However, when you try starting the engine again with engine still at or above 176 degrees F ECM runs both fuel pumps until the engine reaches 400 rpm whereupon the secondary pump is cut off again. This could explain why your engine runs for a few seconds and then dies. You can verify by letting the engine cool down longer then try starting it again to see if the engine runs longer before dying. Be sure to watch the digital coolant temp gauge and note the temp reached.

GOLDCYLON · 04-09-2017

Another possibility is the clutch switch needs to be bypassed. If you type in search a lot of documentation of that process as well. If you had a fuel jumper you could plug it in to determine primary fuel pump beginning of failure.

orthodoct · 04-09-2017

Thanks Jagzpanzer. The only problem with that theory is that the engine should die immediately upon reaching 176 degrees F+/- and it doesn't. It runs just fine at its stable temp of 192 degrees until I turn it off. If I restart it immediately, no problem. If I wait ten minutes, it starts and immediately dies after 3 or 4 seconds with the throttle having no effect. If the pump were seized, it should have drawn enough current to have popped the fuse and it didn't. I have a fuel pressure gauge that I can attach to the Schrader valve and measure pressures, but haven't gotten that far yet. I checked for ECM and CCM fault codes via ALDL connector and there are NONE; either C12 or --- everywhere. Now, I have had a ham radio license since I was 15 and what do you folks think of this theory? Jerry and Mark, need some input here if you have a chance! When the engine is turned off after heating up to full temp, the plenum gets hotter. Could the TPS sensor or the manifold absolute pressure switch be causing symptoms like this??? I thought about the CCM/ECM (the one under the hood!) heating up so I purposely left the hood up with my last test to prevent it and was still able to reproduce the problem. I THOUGHT that I smelled a fried electrical smell coming from the vicinity of the TPS sensor when this first happened, but could have been mistaken. My understanding is that the TPS sensor is just a potentiometer that varies output from about +0.5v at idle to +5.0v at WOT. I checked the fuel regulator, the diaphragm is intact, but sucking on one of the hoses going into the plenum did have a bit more gas odor than I would have thought. The hose to the MAP is intact and the short one going from the regulator to the plenum is new (from Jerry). Checked them both. Starting to really suspect that MAP sensor becoming unstable/defective when heat soaked. Friend Goldcyclon, what is this about a fuel bypass harness that I just saw? Did I miss a group buy or something? Did you get the metric pins for the shock gears that I sent you? Thanks, guys. We'll get this fixed and it will add useful info to our database for when it happens to somebody else. Thanks for the help, as ALWAYS! When that car died, it did so in front of a local repair shop. I had enough sense to have it towed home. Guarantee you that they had never even heard of an LT5 before and mine wasn't going to be their guinea pig. You know, we folks on this forum have become the world experts with regard to that car and you folks on this forum make me feel like a knuckle dragging idiot!!
Thank again!
Ty

karlaw · 04-09-2017

I will be watching close at this post. How do I check fuel regulator, and where is it located ?
My 2 No Start cars are driving me crazy.

Sent from my iPhone using ZR-1 Net Registry

orthodoct · 04-09-2017

Hi Karlaw. Fuel regulator is at back of plenum, has a round black top with a vacuum connection. Fuel lines run into it. It has a sensing diaphragm in it. If the diaphragm is ruptured, it will allow raw gas into the plenum and can't regulate fuel pressure. Best way to check is to see if the hose connected to it has liquid gas in it. It should not. If engine is running and you remove hose and diaphragm is defective, will spray gas so be careful. Gurus, let me know if I am in error.

QB93Z · 04-09-2017

Car starts warm and dies after 3-4 seconds if the primary indication of a failed or failing primary fuel pump. I have had it happen 4 times in my ZR-1's. The pump is easy to change and then you will be able to look for other problems.

Note: I have seen a case where the secondary fuel pumps internal check valve failed intermittently and the primary fuel pump discharged was "short cycled" in the tank. Net result, car would run poorly and sometimes die immediately after a warm start. But it would run great at full throttle because the secondary pump check valve was not a factor with the secondary pump running.

A fuel pressure gauge on the fuel rail during the period when the car was running poorly identified the problem.

Jim

orthodoct · 04-09-2017

Thanks, Jim. I have a fuel pressure gauge. Will check it out. Sounds like failING is the operative term here since it runs fine at partial throttle even when warmed up and secondary pump shuts off if I follow your logic correctly.
Thanks!
Ty

QB93Z · 04-09-2017

BTW, I have seen many failed fuel pumps and have never seen one blow the Fuel Pump Fuse. It has probably happened but I have never seen it.

Jim

orthodoct · 04-09-2017

Thank you, Jim. What would you expect normal fuel rail pressure to be??

Sent from my iPhone using ZR-1 Net Registry

04-09-2017	#1
orthodoct Join Date: Aug 2014 Location: Crossville, TN Posts: 88	failure to start after warmed up Gentlemen: Brand new problem. Car running fine after rebuild. Had my hair cut yesterday and got 92 ZR1 up to operating temp. Got back in car to go home about 30 minutes later. Starts, runs 3 or 4 seconds and dies. Throttle appears unresponsive at that time. Started about ten times then had to be towed home, seventy five bucks wasted! Once cooled down to below about 150 degrees oil temp, started just fine. Suspected fuel problem, but even with problem, Schrader valve on fuel rail is pressurized. Ran diagnostics this AM and no codes are set. Neither FP1 or FP2 fuses open. Fuel pump/sender unit is new and got it from Jerry about a year or so ago. Fuel filter changed when new pump assembly installed. Started this AM and ran up to operating temp of 192. Restarted immediately, but when attempted to restart ten minutes later, once again starts and runs 3-4 seconds and dies. No evidence of fuel starvation at WOT when running. I read about potential problem with loss of primary fuel pump and fact that both primary and secondary pumps run on startup (until 176 degrees I think that I read??) and then secondary shuts down except when secondary injectors come on line. If primary pump dead, would expect fuel starvation at WOT and it is a new unit. 92 ZR1 owned since new, Haibeck chip, new injectors from Jerry, rebuilt everything under plenum, new clutch from Bill Boudreaux, Stainless Works headers with Corsa exhaust. Has run flawlessly for over a year until this happened. What to do??? Thanks! Ty (orthodoct)

04-09-2017	#2
Jagdpanzer Join Date: Apr 2007 Location: Northern VA Posts: 2,661	Re: failure to start after warmed up Sounds like the same problem I had right after acquiring my 94 ZR-1 ten years ago. Turned out to be the primary fuel pump had seized up. When first starting cold the ECM runs both fuel pumps until 176 degree F coolant temperature is reached. Then it cuts back to just the primary fuel pump. If the primary fuel pump is not working the engine will immediately shut down due to lack of fuel pressure. However, when you try starting the engine again with engine still at or above 176 degrees F ECM runs both fuel pumps until the engine reaches 400 rpm whereupon the secondary pump is cut off again. This could explain why your engine runs for a few seconds and then dies. You can verify by letting the engine cool down longer then try starting it again to see if the engine runs longer before dying. Be sure to watch the digital coolant temp gauge and note the temp reached. __________________ Phil Wasinger 1994 Torch Red ZR-1 WAZOO Member George Braml Intake Last edited by Jagdpanzer; 04-09-2017 at 10:49 PM.

04-09-2017	#3
GOLDCYLON Join Date: May 2007 Location: Peoria, AZ Posts: 9,155	Re: failure to start after warmed up Another possibility is the clutch switch needs to be bypassed. If you type in search a lot of documentation of that process as well. If you had a fuel jumper you could plug it in to determine primary fuel pump beginning of failure. __________________ GOLDCYLON - 91 ZR-1 #2014 GOLDCYLON - 90 ZR-1 #2794, 4L60e (Formerly Schrade's) GOLDCYLON - 11 CTS-V Arizona State Director 91 WHITE/BLACK #2014. 380 P&P&PCed,Ported Heads, Jeal Long tubes, Corsa Exhaust/FIKSE FM-5s /LED TLs, LED Headlights, Front Wilwood 6 piston narrowlite calipers and rear Wilwood caliper street shop mod,CNCed Coolant Pipes,TPI Cvr,Filter cover,Stainless Bolts, DRM/DOM PROM /ZFDOC mod build #102,DRLs,BMAD with stainless Debris Screen,Coplan Air Blaster, Pioneer APP Radio 4,Brey-Krause HB,Sub Bar,Fire extinguisher seat mount,DRM Coilovers,LEDs everywhere,Compass mirror (orange),V1 DIC hidden display, Homelink sun visor, Carbon Fiber top x3 and APSIS Carbon Fiber interior, APSIS CF Steering Wheel/NAPA Leather, Banski trailing arms, Guldstrand front suspension,urethane bushings from Prothane (total suspension) ZFDoc drive shaft safety loop, raptor shift light (orange),AO engineering louver front plate, Console seat cushion, 96CE seats with black custom Sheepskins, ss billet catch can,Viper remote entry/alarm,Cragar Rear Louvers,LED side louver lights, Dewitts Radiator with SPAL fans and a Woods 160 T-Stat 90 RED/BLACK #2794. 4L60e Automatic Stage V by RPM Transmission, TCI Dedicated TCM, OBX Stainless Headers, Corsa Exhaust, SAN Secondaries and Haibeck PROM, Exotic Muscle Coil overs, LED Interior Lights, LED Tail Lights, LED Headlights, 94 Sport seats with black custom Sheepskins , Cragar rear louvers, GS Front calipers, Banski Trailing arms, APSIS Carbon Fiber steering wheel, Front and Rear Baer Eradispeeds, DRLs, Guldstrand front suspension,urethane bushings from Prothane (total suspension), Dewitt's Raditor with Dual SPAL fans and a Haibeck 170 T-Stat 11 RED/GREY CTS-V

04-09-2017	#4
orthodoct Join Date: Aug 2014 Location: Crossville, TN Posts: 88	Re: failure to start after warmed up Thanks Jagzpanzer. The only problem with that theory is that the engine should die immediately upon reaching 176 degrees F+/- and it doesn't. It runs just fine at its stable temp of 192 degrees until I turn it off. If I restart it immediately, no problem. If I wait ten minutes, it starts and immediately dies after 3 or 4 seconds with the throttle having no effect. If the pump were seized, it should have drawn enough current to have popped the fuse and it didn't. I have a fuel pressure gauge that I can attach to the Schrader valve and measure pressures, but haven't gotten that far yet. I checked for ECM and CCM fault codes via ALDL connector and there are NONE; either C12 or --- everywhere. Now, I have had a ham radio license since I was 15 and what do you folks think of this theory? Jerry and Mark, need some input here if you have a chance! When the engine is turned off after heating up to full temp, the plenum gets hotter. Could the TPS sensor or the manifold absolute pressure switch be causing symptoms like this??? I thought about the CCM/ECM (the one under the hood!) heating up so I purposely left the hood up with my last test to prevent it and was still able to reproduce the problem. I THOUGHT that I smelled a fried electrical smell coming from the vicinity of the TPS sensor when this first happened, but could have been mistaken. My understanding is that the TPS sensor is just a potentiometer that varies output from about +0.5v at idle to +5.0v at WOT. I checked the fuel regulator, the diaphragm is intact, but sucking on one of the hoses going into the plenum did have a bit more gas odor than I would have thought. The hose to the MAP is intact and the short one going from the regulator to the plenum is new (from Jerry). Checked them both. Starting to really suspect that MAP sensor becoming unstable/defective when heat soaked. Friend Goldcyclon, what is this about a fuel bypass harness that I just saw? Did I miss a group buy or something? Did you get the metric pins for the shock gears that I sent you? Thanks, guys. We'll get this fixed and it will add useful info to our database for when it happens to somebody else. Thanks for the help, as ALWAYS! When that car died, it did so in front of a local repair shop. I had enough sense to have it towed home. Guarantee you that they had never even heard of an LT5 before and mine wasn't going to be their guinea pig. You know, we folks on this forum have become the world experts with regard to that car and you folks on this forum make me feel like a knuckle dragging idiot!! Thank again! Ty

04-09-2017	#5
karlaw Join Date: Jun 2008 Location: Alberta Posts: 85	Re: failure to start after warmed up I will be watching close at this post. How do I check fuel regulator, and where is it located ? My 2 No Start cars are driving me crazy. Sent from my iPhone using ZR-1 Net Registry __________________ LT5

04-09-2017	#7
QB93Z Join Date: May 2007 Location: Westminster, Maryland Posts: 3,689	Re: failure to start after warmed up Car starts warm and dies after 3-4 seconds if the primary indication of a failed or failing primary fuel pump. I have had it happen 4 times in my ZR-1's. The pump is easy to change and then you will be able to look for other problems. Note: I have seen a case where the secondary fuel pumps internal check valve failed intermittently and the primary fuel pump discharged was "short cycled" in the tank. Net result, car would run poorly and sometimes die immediately after a warm start. But it would run great at full throttle because the secondary pump check valve was not a factor with the secondary pump running. A fuel pressure gauge on the fuel rail during the period when the car was running poorly identified the problem. Jim __________________ If it isn't fun, you aren't doing it right! 1990 Black ZR-1 - sold 1993 Quasar Blue ZR-1 1994 Competition Yellow ZR-1 1995 Dark Purple ZR-1 Maryland State Coordinator WAZOO Member

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