90 Z cranks but will not start

[mhobtr]

Originally Posted by Kwood

No. I bought a couple of the suggested fuel pumps and am sending to the local Vette mechanic to let him run the diagnostics. Would love to say I’m a DIY guy, but I don’t have that equipment. Or a garage, after the divorce. But, I still have my Z, so that’s something.


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If he replaces either or both pumps, tell him to make sure the back flow prevent valves are working. I have had two new Delphi pumps that I had to exchange because those valves were not working.


Also tell him to remove all of the plastic hose clamps and replace them with stainless steel clamps, properly tightened to prevent leaks.

[Paul Workman]

Originally Posted by mhobtr

If he replaces either or both pumps, tell him to make sure the back flow prevent valves are working. I have had two new Delphi pumps that I had to exchange because those valves were not working.


Also tell him to remove all of the plastic hose clamps and replace them with stainless steel clamps, properly tightened to prevent leaks.

Good advise...on BOTH counts. I installed new Airtec pumps and the check valve on one was bad out of the box. AND, the plastic clamps were brittle. Steel hose clamps - 7 years ago and counting!

[Reichert]

I learned the importance of properly sized and tightened clamps the hard way: http://www.zr1.net/forum/showthread.php?t=29943

-Stephen 1990 #2288

[TX '90 ZR1]

While you are in the fuel tank I would suggest changing the plastic "Y" out with one of Carter's machined fittings. (Carter200)
25 year + plastic has a tendency to get brittle. Mine had a crack in it.

[cbaclawski]

I don't think this is relevant to the situation described, but posting this for others that may be searching in the future.

After removing the plenum and changing the coils, I had the same problem. Car would crank and crank but not start.

After an embarrassingly long time troubleshooting, I noticed that the connecter plug to the Coil assembly had come unplugged during the plenum re-install. A long screwdriver to push the plug back in later, It fired right up.

Something worth the 10 sec it takes to check and potentially fix, just in case...


Curt

[Paul Workman]

Any updates? Hope you got it going. But, if not, anything those of us "standing around your car", drinkin a brew can suggest further?

.

[Dynomite]

Originally Posted by mhobtr

Quick check is to spray starting fluid in the throttle body and crank the engine. If it fires and stops, you have a fuel problem. If it doesn't fire, you have an ignition problem.

Excellent and simple Diagnostic LOGIC


I have to put that in Solutions

[Kwood]

I do have an update. I went ahead and ordered fuel pumps from a link on the site, got the car and the pumps to my mechanic. He found that the hose and come off but the pumps themselves were fine. Hope that makes sense, I did not get any more details when I picked it up. He did replace the plastic clamps, as was suggested here. Great that there was decent weather here on Sunday and I got to get out and let the beast breathe. Thanks again everyone for the feedback! Great family to be in.


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[dredgeguy]

Originally Posted by Kwood

I do have an update. I went ahead and ordered fuel pumps from a link on the site, got the car and the pumps to my mechanic. He found that the hose and come off but the pumps themselves were fine. Hope that makes sense, I did not get any more details when I picked it up. He did replace the plastic clamps, as was suggested here. Great that there was decent weather here on Sunday and I got to get out and let the beast breathe. Thanks again everyone for the feedback! Great family to be in.


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Had the same issue with mine last year.

[mhobtr]

That's great news.

The ZR1 dual pump setup is precarious.

When both pumps are running, and all in-tank hoses are tight, it works great. If a hose clamp comes loose, part of the pumped fuel will leak back into the tank resulting in lower fuel pressure at the injector manifold.

In a worse scenario such as yours, where the hose comes off, all of the pumped fuel just blows back into the tank resulting in little to no fuel pressure at the manifold.

The most aggravating to me was a bad check valve in the secondary pump. When the engine started, both pumps ran and everything seemed fine but when the secondary pump timed out and stopped pumping, the fuel from the primary pump had a path back into the tank, backwards through the secondary pump, resulting in very low pressure at the manifold. (Took me over an extra hour to get home because I kept "running out of gas". Had to coast to the shoulder, restart and then drive until the secondary pump timed out and I "ran out of gas" again. This created some very undesirable lean conditions).

A bad check valve in the primary pump will result in loss of fuel pressure at the manifold after the engine shuts down and slower starting because the system has to re-pressurize. But other than that, I don't think a bad check valve in the primary causes any other issues. So, if you have one pump with a bad check valve, and you don't have a replacement, install it on the primary. Or install a primary/secondary reverse wiring harness until you can get a proper repair. I keep one of these harnesses in my Z now.