I’ve been having a lot of trouble with my 89 that won’t start. It sat for about three weeks until I recently tried to start it. Had a dead battery, so I jumped it off and it started up. It’s always had a long start and started just like it normally does. I drove it up to the gas station because the fuel was very low. After I cut it off and then tried to start it again, the battery didn’t have enough to fire it off. O’Reilly checked the battery and charged it and told me it’s just fine. Hooked it back up and it cranked over perfectly, but wouldn’t fire. Tried some starting fluid down the intake and it fired but refused to run. I had it towed it back to my garage and started diagnosing. Here’s what I’ve come to so far:

-Fuel pump, fuel pump relay, and injectors have been replaced and are confirmed working properly
-To test for proper fuel pump operation I gave 12 volts to pin G on the ALDL connector and heard it running. Disconnected fuel filter (and replaced it) and ran hose to a bucket and confirmed fuel was flowing while pump was on.
-Check valve inside pump is also working properly. After running the pump with all lines connected and confirming no leaks, I began to disconnect the fuel supply line from the sending unit assembly. As I loosened the hose clamps, the hose began to slide off on its own, confirming there was a large amount of pressure. I pushed it back on to tighten the clamps back down but lost hold of it and got a rocket of pressurized fuel out of that line like you wouldn’t believe. So the check valve inside the pump is not letting pressure back out, neither is the pulse regulator because I deleted it with regular fuel line.
-Even with the fuel pump running and pressure inside the supply line, there was zero pressure at the fuel rail. At first I was using a screwdriver to press the valve and got nothing. Then I used a pressure tester and still got zero.
-When I replaced the fuel filter, I took the opportunity to blow compressed air through the pump-to-filter side of the line, then took off the plenum, runners, and fuel rail to blow compressed air through the filter-to-rail side of the line. The entire length of the fuel supply line is clear with zero blockage or leaks
-To test for a faulty fuel pressure regulator, I disconnected the return fuel line from the sending unit assembly and pinched it off with vise grips. I then ran the pump. Still, zero pressure at the valve. To ensure the pump was building pressure and not letting any back out, I began to disconnect the supply line from the assembly unit again, and guess what, huge blast of pressurized fuel.

I have spent two weeks working on this, delving into these forums to learn these diagnostic procedures and research similar problems and their solutions. Right now it seems as if God Himself is supernaturally diverting all the fuel pressure into the next world, because the fuel lines are clear and unobstructed, the fuel pump is operating perfectly, the pressure regulator isn’t letting pressure out the return line, and there is pressure in the supply line. Yet despite all this, zero pressure at the rail and the car will not fire off and run. It cranks beautifully but will not fire off and run. I’m here to ask for some help from the guys who know more about these cars than me, and I am completely willing to hear any advice whatsoever that may help me get this car running. I’m young and stupid and I could use some wisdom from the guys who have known the TPI since it was new. Ask me questions, ask for pictures, anything at all. Any help is much appreciated,

-Alex

 

You may be young but you're not stupid. Your debug and trouble-shooting is actually pretty good. But something is wrong physically with the fuel path.

I'd replace that FP regulator diaphragm no matter what you think about its state. My '89 fuel pressure regulator when I replaced it February was already a disintegrating rubber mess.

If you have zero pressure at the rail, there are only a few possibilities. 1/ the FP regulator is not letting any pressure build at all and the fuel is just returning to the tank without firing properly into the injectors, or 2/ there is a physical obstruction in your fuel supply line either before / after the filter or in the rail itself. I suppose it's not impossible that the rail is blocked at the input line side, but that's highly unlikely...

Replace the regulator diaphragm and start there I'd say....

Others?

 

This might not be the same as mine is a 96. When I replaced my regulator I remember a fine screen in the intake. If your filter had busted inside this screen (if you have it) may be clogged. Dan

 

To my knowledge the '89 regulator does not have a filter screen, at least not that I saw...

 

First get a Fire Extinguisher and keep it handy when working on the fuel system. Fuel mist is EXTREMELY Flammable...!

I would start at the Fuel Pump Relay and go through the wiring. There is a tool called a Power Probe and it allows you to have either 12 volts or ground at the tip based on the rocker switch's position. I would use something like the power probe and put 12 volts into the wire that feeds to the Fuel pump. That should get your pump working, if not go to the panel over the fuel tank and remove it. This allows you to access the 3 wires that go to the Fuel Pump Sending Unit and gas gauge. The large red wire feed power to the fuel pump, the middle wire is the return signal for your gas gauge and the last wire is the Ground wire.

I would clearly replace the diaphragm in the FPR as it is a part that breaks down due to the Ethanol. Our Corvettes were made before the Oxygenated fuel was thought of, it destroys anything with rubber in it over time. Including rubber hoses!

Our Corvettes need a good solid battery and CLEAN battery and power connections. I once found a missing ground strap when replaced allowed my power antenna to work again! Make sure that your engine is well grounded. To do this put your multi-meter on the DC Volts setting and put the red wire on the battery Positve, then take the negative lead and touch metal on the engine. You should see the same voltage in both places. Take a moment and tell me what your Fuse Panel Voltage is as well, please. The post supplies the Fusible Links with Battery Positive and then it goes to the fuse panel. From the fuse panel it is distributed all over the Corvette. I saw a close to 2 volt voltage drop through the post being all corroded. Everything was getting 10 volts versus 12 and that makes a BIG difference as my fuel pump ran slower and the radio wouldn't work. A simple cleaning brought 12 volts to everything once again.

Have you tried to see if gasoline is flowing through the fuel filter? This is where I tested my lines on my C4. In the past we have seen some partially plugged fuel filters as well. I learned that right behind the Passenger's seat is a low spot on the Fuel Supply line. This blocked off the volume of fuel going through but allowed me to see pressure at the fuel rail. When running it just would not rev at all as it was not getting enough volume of fuel. The Ethanol caused my fuel line to rust shut internally thanks to it absorbing water which then goes to the low spot and starts rusting.

If you have the fuel Pump "running" and you still have nothing in the fuel rail then it is likely you have a blockage in your fuel lines. I had to replace both fuel lines on my 1988 C4, one Fuel "Supply" line and one Fuel "Return" line.

Being Young does not make one stupid or anything negative, and here on the Corvette Forum there are NO "Stupid" Questions. When I was in college I thought all older people with white hair were smart, 4 years years in Fort Myers, FL taught me different.

We are here to help each other..... We are fellow Corvette owners trying to help those who need it or have questions. I know Early C3's and the L98 equipped C4's moderately well. You are going through the same problem I had years ago so that might be a good reason to help save you some aggravation.
Have an awesome Day!

 

Alright, so I have an update.

The FPR diaphragm has been replaced. After replacing it I connected the fuel pressure tester to the valve and started priming the system by turning the key to the ON position about 7 or 8 times. After seeing the pressure gauge read absolute zero yet again, I jumped 12 volts to the fuel pump via the ALDL connector and ran it for about 10-15 seconds. Still reading zero pressure.
Since I know the lines are perfectly clear and leak free, I decided to remove the FPR again and check for blockages in the rail itself. To my amazement and further confusion, there was significantly pressurized fuel inside the regulator. Thankfully I got it under control and cleaned up the mess. So now here’s an updated summary of my situation:

-Fuel pump and fuel pump check valve verified working and making good pressure
-Both fuel lines (supply and return) are clear, zero blockage
-Supply line pressurizes and holds pressure
-FPR pressurizes and holds pressure

…and yet…

Zero pressure in the fuel rail. Literally nothing from the valve.

I’m getting pretty sick and tired of taking apart the plenum and runners to get the fuel rail out, but it seems I’m going to be doing it again. From everything I have diagnosed, there is pressure being built and held perfectly right up to the FPR and then absolutely nothing in the rail. I’m going to remove it again to thoroughly inspect it to see what the holdup is. I can’t fathom any other problem than something blocking the fuel feed from the FPR to the rail. You guys may be able to understand my confusion and frustration after verifying a perfectly clear path of fuel to the rail, and then getting absolutely zero pressure.

 

Change the valve seal. Just like a tire. I bet it is clogged. Dan edit: I don't know if one from a tire shop would work with gas.

 

That time you spent replacing the regulator diaphragm was not wasted, trust me. It needed to be done on a car that age.

If the regulator has pressurized fuel in it, then your fuel rails have fuel pressure in them. The FP regulator receives its fuel from the fuel rail itself. The whole rail (both sides) get the fuel supply line pressure from the inbound line, both left and right rails get fuel from that gray cross-tube in front, then the FP regulator holds pressure in the rail until it reaches 40-ish PSI - then releases any excess pressure into the fuel return line (that gray tube on top of the rail). That fuel goes back to the tank.

If your Schrader valve is defective somehow, and not letting fuel get to your pressure gauge, then that's the only way you can have pressure in the rail / regulator / return line and still see zero fuel pressure. You said that you used a screwdriver to press the center probe and that didn't work, then now you're using a FP gauge and hose right?

 

Your pressure gauge is broken.

 

Schrader or gauge---has to be.

 

Be careful taking out the scrader valve if the rail is pressurized.

 

If you have a cheap, Harbor Freight or Amazon gauge, look at the o-ring on the screw on fitting. If it is white, thick, nylon, your gauge is likely not threading deep enough to press your valve.
Back when I did AC work, the Orings in those pressure gauge hoses were small, thin, black, soft rubber. They would not last more than a couple of summers, but the hose would thread on deep enough to press and make a seal.

 

The pressure gauge I’m using is loaned from O’Reilly. They gave me a brand new one to use. I verified the pressure gauge and schrader valve are working properly by doing this:
Disconnected the fuel rail and took it out completely, left the injectors in it. Connected the pressure gauge to the valve. Since I had the FPR unit removed, I plugged both holes through which fuel travels to it and also plugged the return line side of the rail. This way, the only escape for air would be through the valve. The pressure gauge has a relief valve to let pressure escape. While blowing through the supply line with all other holes plugged, I pressed the relief valve on the pressure gauge and air flowed right out perfectly fine. So my schrader valve is working properly. I doubt the brand new pressure gauge is faulty, seeing as I used a screwdriver to depress the valve before and got nothing that time too.
I have checked, re-checked, and triple checked every component of the fuel feed and return system to ensure there is absolutely zero excuse for pressure to escape, but I’m still getting zero fuel pressure. And of course, it doesn’t start when I crank it. I’m racking my brain to come up with some scenario that would cause this to happen. Right now what comes to mind is the fuel lines possible being reversed at their connection to the rail. Tomorrow I’m going to run the pump with the lines disconnected to ensure without a doubt which line is which and I’ll give an update.
And you’re certainly right ajp01, that old FPR diaphragm was rotten!

Last I remember I reconnected the lines precisely as they were when I first disconnected them to change the injectors. That was the first time I messed with the fuel lines. Is it possible that someone before me could have switched the lines to the wrong connections, and the car still ran in that configuration? Or it could be that I fixed the problem by changing the injectors, FPR, or something else, and then created a new problem as I put the car back together by mixing up the fuel lines. Usually problems like this have one of those “simple, stupid” solutions, so I’m hoping that’s what caused it.

Thank you all very much for your help and advice, it’s been invaluable

-Alex

 

You don't have to do that. I have never considered this possibility, but this is the most likely answer to your problem. On the '89, the fuel lines and O-rings at the connections are exactly the same size. I figured this out a few months ago when I did mine; the factory parts diagram calls out two different part numbers for the O-rings (with different diameters) but the documentation is wrong. Some '89 models (at the very least, maybe all of them) have the same size lines and O-rings for both the supply and return.

https://www.corvetteforum.com/forums...gs-1989-a.html

Yeah, ask me how I know...

No, it would never work.

Yes, yes it is. Here is a picture of what they should look like connected. The line with the ribbed protection coils wound around it is the fuel supply line, and it should go to the rail directly. The other line, the one without the windings, should go to the gray tube (return line) on top of the fuel rail.

 

A word of counsel here. You'll need new O-rings for those fuel hookups now, and if you've been removing / reinstalling the FP regulator, injectors, and anything else with an O-ring, you need a whole new kit of fuel rail O-rings for those as well. Lubricate them when installing with a light film of engine oil. This is one area where you want the rings to be fresh, new installs when you're putting everything together the final time.

There are several members here who have had a car catch fire (or nearly) when an O-ring that was nicked due to handling has failed. Even old O-rings that haven't been messed with will fail occasionally.

Don't skimp here and best of luck with everything.

 

I've got braided steel lines going to the fuel rail on my miniram. I have accidently reversed them I can assure you the car doesn't start. It sounds like you have solved your problem.

 

Alex, were you able to get this sorted?