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Discussion Starter #1 (Edited)
No start - No fuel pressure

Roadmaster wagon won't start.

1. had been running fine, then coming out of a store vehicle started but ran very rough and couldn't clear it up with tapping the throttle. Restarted and did same a couple of times. Then quit starting all together.

2. towed it home and began checking obvious things

3. has fuel

4. get a tiny amount of fuel at the schrader valve

5. Has 7volts at relay with key on

Any ideas?

Todd
 

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Roadmaster wagon won't start.
Any ideas?
Todd
Reason the pump doesn't shut off after 2 seconds is because it never builds pressure. You can put 12v to the red jumper lead under the hood to power the pump (handy for draining the tank) and see if that works. IF the pump is actually on and pumping, it could be a collapsed or massively clogged filter, or a line popped inside the tank from your pump.
 

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Roadmaster wagon won't start.

....

4. get a tiny amount of fuel at the schrader valve.

...

Todd

Ok call me out to lunch, but I thought gas out the Schraeder was a broke diaphragm (hence fubared FPR). Set me straight.
 

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Ok call me out to lunch, but I thought gas out the Schraeder was a broke diaphragm (hence fubared FPR). Set me straight.
The Schrader Valve is on the Fuel Rail and is what you use to test Fuel Pressure. I have replaced mine with a Pressure Gauge. So it's full on 47 P.S.I. at this valve on a functioning car. The FPR is kinda isolated away from this valve.

Roadmaster wagon won't start.

4. get a tiny amount of fuel at the schrader valve.

5. fuel pump stays on with key on (doesn't shut off after 2 second prime)

Any ideas?

Todd
I suspect a couple of things...

On #4 - If you have normal Pressure (approx 47 PSI) and it holds pressure after shutoff, you will see quite a Bit of fuel pressure when pressing the valve. It will spray out pretty good. Not seeing much there tells me you got a low Fuel Pressure issue. Did you put a Gauge on the vale to see what the Pressure is there?

On #5 - You use the Test Lead to bypass the 2 sec. Prime circuit. Using this just bypasses the Fuel Pump Relay. If the pump is running continuously, I suspect you have a bad/stuck relay and/or a bad wire/connection in this circuit.

In general, I suspect you have a bad Fuel Pump or In-tank wiring issue. There are numerous threads on how you can isolate this circuit to confirm all is well before dropping the tank. Most issues with FP are usually inside of the tank. I also suspect as someone mentioned, it could be a blockage in the filter or even a broken hose inside the tank that is causing a majority of the fuel to just blow back into the tank and not make it to the Rail. I once had the plastic lid on the FP break and when running the pump could hear gas just blowing right back in the tank.
 

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Discussion Starter #5
Thanks 4DoorSS....new info is that what I thought was the fuel pump running was actually the rear wiper motor (arm is disconnected) - somehow the switch got turned on. It sounds like a fuel pump when standing at the front of the car.

atlantadan - there is no pressure feedback on these systems to turn off the pump after they prime....its time only.

96 Black - you are thinking of a failed diaphragm when you pull the vacuum line to it and get a bit of fuel out.

Todd
 

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you need the tools member !

fuel pressure gauge with a drain valve on it . a wire with a 10amp fuse set on the prime wire .hook up pressure gauge then setup the power to prime wire at the under hood fuse box area.. red wire ..

fuel should be 41-47 psi. this is the spec .. now you open the drain valve set it up so fuel gets into a container .. does the fuel flow robustly ? if not then a restriction..

if fuel pressure is below 40psi keep the fused jumper on the prime wire get the voltmeter out NOT SOME TEST LIGHT and check for volts in the rear . volts should be 11.5 volts if the volts are less than 10 volts pump may not pump good .. 8 volts no pumping ..that is with the pump running when you check the volts .. no pump running then the volts should match the battery volts.

you have gas in the tank ? if you have less than 1/3 tank indication good chance little bit of gas fumes LOL..
 

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Thanks 4DoorSS....new info is that what I thought was the fuel pump running was actually the rear wiper motor (arm is disconnected) - somehow the switch got turned on. It sounds like a fuel pump when standing at the front of the car.

atlantadan - there is no pressure feedback on these systems to turn off the pump after they prime....its time only.

96 Black - you are thinking of a failed diaphragm when you pull the vacuum line to it and get a bit of fuel out.

Todd
Ok, well use the Prime overide wire to keep the FP circuit hot for more than 2 seconds and see if the pump is running. If not, try to hit the bottom of the Fuel Tank a few times and see if it activates....if not, mostlikely in the tank. If it does startto work...you till have a problem in the tank, either a bad pump and or in tank wiring/burnt wiring/bad connections. I've had all of the above.

Now go back to the 3 wire Plug back at the rear bumper and unplug this connector. Using a Meter, check for 12 Volts across the Gray and Black wires in this connector. If you have 12V (or close to it) on these 2 wires, then the problem is definetly in the tank.

DID YOU TEST FOR FUEL PRESSURE AT THE SCREADER VALVE? You probably dont need to worry about that until you are sure the pump is at least running first.

EDIT - Sorry, just saw this was a wagon. Not 100% sure where that plug is for the Sending unit on those cars but you should be able to find it at the front or back of the tank and follow the wire harness til you find the plug. I think some care (caddy?) have 4 wire connector but blieve the color for the pump is the same - Black for Ground and Gra for Hot.
 

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atlantadan - there is no pressure feedback on these systems to turn off the pump after they prime....its time only.

Todd
Learned something new today! LOL

Regarding what 4DoorSS said, the connector for the pump harness - on my wagon - was on the rear side of the car / back side of the tank. Opposite side from the sending unit lines.

I also noticed that you said you've got 7v at the relay. If I had my car here I would test, but to me that seems low. What about at the #2 fuse in the underhood fuse box? For all I know, however, 7v could be normal.
 

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...
96 Black - you are thinking of a failed diaphragm when you pull the vacuum line to it and get a bit of fuel out.
Todd

The Schrader Valve is on the Fuel Rail and is what you use to test Fuel Pressure. I have replaced mine with a Pressure Gauge. So it's full on 47 P.S.I. at this valve on a functioning car. The FPR is kinda isolated away from this valve.
......

Ah soooo, thanks.
 

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Roadmaster wagon won't start.

1. had been running fine, then coming out of a store vehicle started but ran very rough and couldn't clear it up with tapping the throttle. Restarted and did same a couple of times. Then quit starting all together.

2. towed it home and began checking obvious things

3. has fuel

4. get a tiny amount of fuel at the schrader valve

5. Has 7volts at relay with key on

Any ideas?

Todd
Ok Todd, looks like you changed your Original Post and now #5 is different. You may want to just leave that 1st post alone and update the thread as you discover things or it could get confusing following this thread.

Anyway, so just having 7 Volts at the relay is a problem and youre on the right track . You should be seeing 12V there. I attached a link to a schematic for the 94-95 Impala in case you need it and it could help you trace out some wires and do testing. I'm assuming that the roady wagon is very simlar to the Impala.

http://www.goldsswagon.com/diagrams/impala_9495engine_3of3.pdf

With 7Volts "at the Realy" where exactly is that? Cause as you can see in the schematic...its pretty much 12V going straight to the relay. As I suspected all along you have some kind of wiring issue going on that you need to isolate. You will see voltage drops across some components and wire length but you want to see as close to 12V back at the tank as possible. Low voltage can also affect Fuel Pressure. Also having the racetronix Hotwire kit on my car, I know that the FP increased a few pounds with more volts back there and dropped slightly when switching back to Stock Only.
 

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try gently removing the vacuum line from the fuel pressure regulator on the rear of the engine's fuel rail and see if fuel is coming out. That would also tell you that the diaphram is broken and you would need a new fuel pressure regulator.
 

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try gently removing the vacuum line from the fuel pressure regulator on the rear of the engine's fuel rail and see if fuel is coming out. That would also tell you that the diaphram is broken and you would need a new fuel pressure regulator.
reaboy did not post any more about his no start . probably has no gas in the fuel tank .
 

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He said it "has Fuel".
 

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Discussion Starter #14 (Edited)
j cat - always a joker in every crowd.....if not constructive, then think it, don't type :) Thanks for your first message though. I have a fuel pressure gauge but don't need it at the moment until fuel will come out of the schraeder

The reason I edited the post was what was thought to be the pump running continually after keyup was actually the rear wiper motor. When I was underneath to check the racetronix harness/relay I could tell the electric motor sound was not the pump. Some of my dash panels are out (including the rear wiper switches) and apparently that is switched on with no way to turn it off until I reinstall the switch front - or open the rear hatch which is what I did.

I haven't had time to revisit the no fuel issue but plan to get to it later today.

Next step is smacking the tank to see if the pump can be coerced into running. The low voltage is obviously an issue so that needs to be traced also. Hot wiring to the fuel pump test connector did not turn the pump on either.

Thanks All
Todd
 

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j cat - always a tool in every crowd.....if not constructive, then think it, don't type.
when members do not post back the failure cause , but ask questions , not gonna help other members..

IMO no response on your work ,, good ! one way info to Iowa .
 

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I see "has fuel". Is that because the gauge has 1/4 tank showing? Or, did you actually put an extra 5 gallon can in it? If you haven't added gas, do that FIRST.
 

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j cat - always a joker in every crowd.....if not constructive, then think it, don't type :) Thanks for your first message though. I have a fuel pressure gauge but don't need it at the moment until fuel will come out of the schraeder

The reason I edited the post was what was thought to be the pump running continually after keyup was actually the rear wiper motor. When I was underneath to check the racetronix harness/relay I could tell the electric motor sound was not the pump. Some of my dash panels are out (including the rear wiper switches) and apparently that is switched on with no way to turn it off until I reinstall the switch front - or open the rear hatch which is what I did.

I haven't had time to revisit the no fuel issue but plan to get to it later today.

Next step is smacking the tank to see if the pump can be coerced into running. The low voltage is obviously an issue so that needs to be traced also. Hot wiring to the fuel pump test connector did not turn the pump on either.

Thanks All
Todd
Ok, before even hitting the tank and based on some of the other items yu mentioned that are out, I "suspect" a bad Ground Connection somewhere. This could explain the low voltage readings as you are getting a ground from another circuit. I once had a hood light acting all kinds of strange and it was a broken ground wire going to the Cylinder head.

There are a few grounds at the head and also a few down behine the Kick Panel Covers on both front foot well areas. These are know to get loose and especially at the cylinder head can break. I would inspect all those closely and really recommend you pull them all off, clean the connection area ofall rust/dirt and reassemble with some dielectric grease. Good idea to do this on these old girls anyway.

Bottom line, check your schematic and get your meter out and start checking key points til you find why you are only getting 7 volts where ever that area is that you were seeing 7 volts. As you know, you need to at least see 11V or so back at the Fuel Pump connector. Be careful where you are connecting the meter to ground. If you just touch the Chassis and not the actual ground pin, you may get a false positive. The grounds in these cars were always weak and get worse with time and vibration.
 

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Check the connector under the center rear bumper of the car. Over time, these corrode badly. Disconnect it ... if the copper terminals look green, it's corrosion. Clean it or replace it. You can hot wire the 12v connector at the fuse box and measure the voltage at this connector under the car, but you need to have a load on it (the fuel pump draws a few amperes). The 12v lead might be happy, but the ground could be bad. Instead, hot wire 12v and ground to the pump wire directly (under the rear bumper) and verify that you hear the pump running and that fuel is returning into the tank. Hook up a fuel pressure gauge if you think you are good, but want to be sure. If that is good, then you can rule out the pump and fuel pressure regulator and go find a wiring issue (likely a connector or ground). As these cars age, the dielectric grease in the connectors dries out and stuff starts to corrode. This pump connector is exposed to everything back there under the ass of the car and are an easy target for corrosion.


Note ... if you have been running the FP at a low voltage for an extended period of time (say due to connection or corrosion issues), you will weaken the pump from overheating.
 

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Reason the pump doesn't shut off after 2 seconds is because it never builds pressure. You can put 12v to the red jumper lead under the hood to power the pump (handy for draining the tank) and see if that works. IF the pump is actually on and pumping, it could be a collapsed or massively clogged filter, or a line popped inside the tank from your pump.
A bit off topic. Have you drained the tank that way? How long does it take to drain say 1 gallon? Thank you.
 

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This thread is coming up on 2 months old. I hope the OP got it figured out.

A bit off topic. Have you drained the tank that way? How long does it take to drain say 1 gallon? Thank you.
I have drained the tank this way. It goes pretty quickly. I didn’t time it. I was pumping into 5 gallon cans and I’m pretty sure it was filling them in a minute or two. It went way better than trying to siphon the tank out.
 
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