1991 ZR1 Restore - Help!

[Corvette95]

My 2 cents.... Sounds like you should consult a shop with Corvette (C4) experience. I would not keep trying to crank it. I would verify all the work you just performed is not part of the issue. I also agree that the plug wires could be crossed up as well I know you said you replaced them one at a time but verify with the service manual) . I would also check the DIS connections..how did you unplug and reconnect the DIS? Also, I would get a fuel pressure tester and connect to fuel rail and jump the fuel pump connector (under or around brake booster and make sure you have fuel pressure as fuel lines could have come off in the tank or similar issue) . Don't make the mistake of saying I just fixed that and assume it is all working. Any ZR-1 owner needs two things... Factory Service Manual and Tech1 scanner ( a generic OBD1 scanner will make do until you can find a Tech1 -they are getting very pricey now). The more you do to it, the more you have to recheck. VERIFY and repair... don't guess at it. Again, just my two cents.

[Young1]

Let?s back up a bit. Since you had the plenum off are you sure the connectors are all installed correctly? Two on rear and two underneath. Fully seated, latched, no pins bent. Some times mechanic hacks break the tabs.

I know you have replaced fuel system parts fine and dandy but does it have the correct fuel pressure at the rail? You may have a fuel pressure leak inside the tank.

[kapkanimd]

To clarify, the car was running and idling normal. The only issue I had while it was running is that it would bog down some with revving it up. I double checked the fuses today and did notice FP2 fuse under the dash was blown. I reinstalled a 15a one (I saw that was recommended when changing to Suburban pumps). However, that did not change anything (still won't start).

I am still waiting on the fuel pressure gauge to get here and will test that asap.

Connectors were verified as locked via their clips before I closed up the plenum, but can certainly check if any popped loose. I can also check wires (best I can without removing the plenum again just yet), but I dont that fits the best here (plus no check engine lights or codes on the MT2500)..

Thanks again for all the feedback. I did order a Crank position sensor just because it was cheap and not too difficult to change.

[Corvette95]

soooo. describe how you got the DIS wiring off and ON .

[kapkanimd]

Soooo...... realized I can just do one of the loaner tools from local auto parts store. Hooked up the gauge no reading. Jumped the pump wire (heard pumps running), but still no reading. Thought maybe just bad connection for valve, but manually activating the schrader valve (with pumps running) had minimal fuel coming out (there was no fuel coming out manually before jumping pumps).. Just to be 100% I sprayed some starting fluid in, and the car started right up... FML

So now the question is, why would I all the sudden loose fuel pressure... clogged fuel filter? The pumps are working, I guess I can pull the assembly out again to see if an internal hose came off somehow.. The fuel pressure regulator is a new retrofit from Phil on this forum, and as mentioned 2 new fuel pumps, and new fuel filter.. Granted the system was garbage before this process.. I did not replace the fuel pump assembly which had some rust on it, but seemed to be functional after a thorough cleaning (fuel gauge in car does work as well)


***I am currently following the instruction on how to test each pump at the wire harness connected to the sending unit. I will also pull the unit to see if any hoses are loose - will report back shortly



Sorry for the unnecessary rabbit hole I was leading everyone down.

[HAWAIIZR-1]

Originally Posted by kapkanimd

Soooo...... realized I can just do one of the loaner tools from local auto parts store. Hooked up the gauge no reading. Jumped the pump wire (heard pumps running), but still no reading. Thought maybe just bad connection for valve, but manually activating the schrader valve (with pumps running) had minimal fuel coming out (there was no fuel coming out manually before jumping pumps).. Just to be 100% I sprayed some starting fluid in, and the car started right up... FML

So now the question is, why would I all the sudden loose fuel pressure... clogged fuel filter? The pumps are working, I guess I can pull the assembly out again to see if an internal hose came off somehow.. The fuel pressure regulator is a new retrofit from Phil on this forum, and as mentioned 2 new fuel pumps, and new fuel filter.. Granted the system was garbage before this process.. I did not replace the fuel pump assembly which had some rust on it, but seemed to be functional after a thorough cleaning (fuel gauge in car does work as well)


***I am currently following the instruction on how to test each pump at the wire harness connected to the sending unit. I will also pull the unit to see if any hoses are loose - will report back shortly



Sorry for the unnecessary rabbit hole I was leading everyone down.

As Young1 mentioned you need to ensure your pumps have pressure and not losing pressure in the tank.

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Any chance the plastic old and brittle Y connector is cracked during fuel pump replacement or otherwise? Carter200 sells the replacement piece above that a lot of folks have upgraded to. The photo mine to replace as preventative maintenance.


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[kapkanimd]

Pulled out the sending unit, hose popped off the primary fuel pump.. Connected it, and it cranked right up I connected the pressure gauge back up, and it is only showing about 18PSI.. No change in pressure throughout the rev range, which I do not think it is how it is supposed to work. Not sure if it is this gauge I got from O'Rileys or if something else is wrong.

However, it is still running awful when you try to add throttle. Here is a video I just recorded: https://youtu.be/JTs3TFz8c38 . Ignore the exhaust leak, I am replacing the rusty H pipe that was on it.

This car has not run in probably four years or longer. It definitely smoothes out some as it warms up. I am wondering if it will just take time to clear up. I have some valve cleaner I want to run through it, but just waiting to get the car back on the ground and out of the garage.

Also in the video you can see the tach issue I am having. I didnt hook up the OBD1 this time but will tomorrow.

[dredgeguy]

I had a similar issue and found a fuel hose hanging when I pulled the fuel pumps out to check them. Replaced the plastic clamps with stainless steel to be sure they stay in place. Wish I had also replaced the Y with Carters upgrade but that is for next time. Looks like your making progress....stay at it, you will get it up and running right.

[JG95ZR1]

Does it hold fuel pressure at all when you turn the car off ? Could be a fuel pressure regulator or a pin hole in the pick up tubes in the sending unit. One of my cars had that issue


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[JG95ZR1]

Make sure fuel filter is also installed in the right direction


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