I have a 4.9 conversion and installed a Cadillac Fuel Pump to match the engine requirements. The pump started whining at half a tank, and I replaced the pump and strainer with a brand new unit. The problem continued and I posted the problem here, and the consensus was to replace the Pulsator. I dropped the tank again, replaced the pulsator with a brand new one and new gas hose. Today, it did it again, with the tank full! I ran out of gas with a full tank. I let the engine cool down for an hour, and now started fine, no noise from the fuel pump, and it runs fine. Whatever is happening seems to be when the engine is been running for a while.
Need help to figure this out. Thanks.
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07:25 PM
PFF
System Bot
phonedawgz Member
Posts: 17104 From: Green Bay, WI USA Registered: Dec 2009
If the fuel pump is submerged and the hoses are tight then I'd look for 1) a fuel line close to a heat source that's causing vapor lock. The fuel actually boiling due to excessive heat next to a fuel line. Or 2) the return line either hooked up incorrectly or blocked so that the pump is being deadheaded.
What is your fuel pressure? What is the pressure when it makes the noise?
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09:08 PM
Dennis LaGrua Member
Posts: 15827 From: Hillsborough, NJ U.S.A. Registered: May 2000
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
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09:09 PM
jackcastro Member
Posts: 620 From: WESTON,FL,USA Registered: Dec 2005
Thanks everyone. It is a whining noise similar to when you are running out of gas, but when the tank full. In fact, it did it to me today right after filling up the tank. About vapor lockup, the only hoses near a heat source are the ones going to the overflow tank. Could these cause the problem?
About the relay, I thought it would either work or not. Also, if the relay is bad, the pump will not cavitate but simply shut off.
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09:19 PM
phonedawgz Member
Posts: 17104 From: Green Bay, WI USA Registered: Dec 2009
I'm wondering if the trouble is perhaps the fuel pressure regulator giving out and providing any back pressure. Perhaps it just lets all the fuel flow back to the tank. If you can get the trouble to occur and then pinch off the rubber part of the return line when it's happening and the fuel pressure goes back up then that would say its the regulator.
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09:22 PM
josef644 Member
Posts: 6939 From: Dickinson, Texas USA Registered: Nov 2006
If you have an 87 or 88 the steel lines that go to the expansion tank, and from the expansion tank to the charcoal canister on the driver side of the car are about 4-5 inches from the forward exhaust manifold. How close? This bolt is 5 1/2 inches from the exhaust manifold
mounted on the firewall:
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09:30 PM
joshua riedl Member
Posts: 1426 From: watertown wi USA Registered: Jan 2004
I had this same problem. My tank was severely rusted and the baffle was sliding back and forth. I got a new tank from the junkyard and the pickup assembly was in better shape than mine. I did reuse my fuel pump and the noise has not returned. I don't know exactly what was causing it, I assumed it was the baffle moving around and blocking fuel. First I would look at the tank and see if it's damaged at all. The pickup sits pretty low to the tank and it could be getting blocked.
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09:34 PM
jackcastro Member
Posts: 620 From: WESTON,FL,USA Registered: Dec 2005
The baffles are fine. The tank has no rust at all. I will check the fuel regulator too. I understand that vapor lock would only be a problem on the lines coming to the engine. The onl;y lines close to the exhaust are the ones going to the overflow tank, but I will try to shield them anyway. I will also change all the hoses. Do not know what else to do.
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09:45 PM
phonedawgz Member
Posts: 17104 From: Green Bay, WI USA Registered: Dec 2009
It doesn't matter what happens to the gas in the lines once it leaves the fuel pump - re vapor lock. The pump should produce enough pressure to push any gas in the lines that might have evaporated back via the regulator to the tank. Your pump is new so it should have no problem with providing enough pressure to supply the overflow pressure needed for the return line to function properly.
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10:49 PM
jackcastro Member
Posts: 620 From: WESTON,FL,USA Registered: Dec 2005
with no backpressure the pump's speed might be increasing and you could be taking that noise to be the change in tone.
If the fuel pressure regulator is the problem then perhaps the fuel pressure regulator is what is failing when it gets warm.
I'm just grasping at straws here. One thing I always think about is Sherlock Holms. He said when there is only one possibility left it has to be that one possibility. I have found usually when there is only one possibility left, it's not that possibility, but instead it's that I haven't totally understood the problem and it's actually something else. It's actually one of the reasons i really don't like the books/movies
[This message has been edited by phonedawgz (edited 10-21-2010).]
I have the same problem on my 86 GT. i filled it up went 100 mi. out of gas. (so I thought) when I drive it over 30mi. it gets loud like It's out of gas. let it sit and it ok.
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12:19 AM
phonedawgz Member
Posts: 17104 From: Green Bay, WI USA Registered: Dec 2009
With the pick up pre-filter canoe on the fuel pump pick up there's no way the pump intake can get plugged up and then become unplugged. You replaced everything else. I doubt you have two things that are somehow failing the exact same way.
The key will be to do the fuel pressure test when it fails and then pinching off the return. That will tell you what is happening. I am just guessing at ideas so I wouldn't be surprised if I am wrong.
If you buy the 15.99 fuel pressure gauge from Harbor Freight, you can also use it to drain the fuel off the fuel pressure regulator. Just use the hose that has the end that screws on to the schreader valve. Then on the other end use a short nipple piece of 1/4 water pipe. That will screw into the fitting that the gauge normally screws into. Then screw one of the other ends of hose that come with the gauge, and then run fuel line down to a gas can. Then you can listen to what the pump sounds like when there isn't a restriction to the pressure. Perhaps that will give you a clue if the noise you are hearing matches with a 'no restriction' noise. Again, I'm just guessing at this so I wouldn't be overly surprised that this isn't what is happening.
I used the tubing setup listed above to drain the tank when I had problems but the pump still ran. Just jumper power to the pump and let the fuel pump push all the fuel out of the tank.
I don't mean to jack this topic. it's a 86 GT 4 speed manual. i let it sit for few minutes and turned key on. it sounds like it was running fuel in the tank. the psi gose back to around 10 psi after 15 minutes.
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08:31 PM
jackcastro Member
Posts: 620 From: WESTON,FL,USA Registered: Dec 2005
First of all let me say that I installed a $130 pump, no cheap at all, new pulsator $22+. Today I installed a new fuel pressure regulator($64), and after the car warmed up and ran it on the highway, the pump started whining and the engine stalled. I checked the valve on the fuel rail, and I had air, not gas. Is this vapor lock due to heat? Saturday I will change all the fuel lines (tube and hoses) as a last attempt to fix this. I will wrap the fuel lines with header wrap to shield it from the heat. I do not know what else to look for. Any other ideas?
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09:05 PM
PFF
System Bot
Oct 22nd, 2010
darkhorizon Member
Posts: 12279 From: Flint Michigan Registered: Jan 2006
I believe that what dark is getting at is that the tank venting system may be clogged. You also might want to try a simple test. Disconnect the fuel line after the fuel filter. Put a long hose on it and run it into a gas can. Now unhook the yellow fuel pump connector at the firewall. Using the two outside end pins (black is gound) directly apply 12 V power but do it in a way that there will be NO SPARK. See if you have a steady and fast fuel flow. If you do not the problem is between the fuel pump and the end of the fuel filter. If you have a good fuel supply then the problem is probably the regulator.
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08:35 AM
phonedawgz Member
Posts: 17104 From: Green Bay, WI USA Registered: Dec 2009
Originally posted by Dennis LaGrua: I believe that what dark is getting at is that the tank venting system may be clogged. You also might want to try a simple test. Disconnect the fuel line after the fuel filter. Put a long hose on it and run it into a gas can. Now unhook the yellow fuel pump connector at the firewall. Using the two outside end pins (black is gound) directly apply 12 V power but do it in a way that there will be NO SPARK. See if you have a steady and fast fuel flow. If you do not the problem is between the fuel pump and the end of the fuel filter. If you have a good fuel supply then the problem is probably the regulator.
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11:11 AM
phonedawgz Member
Posts: 17104 From: Green Bay, WI USA Registered: Dec 2009
Harbor Freight has fuel pressure gauges for $15.99. It really would be good to know what is happening with the fuel pressure with the return open and blocked when this happens. Also good would be to read the voltage on pin G during when the problem is happening. What do you do to get the problem go away?
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11:15 AM
phonedawgz Member
Posts: 17104 From: Green Bay, WI USA Registered: Dec 2009
I was just about to say that also but to save money and time guessing just get a fuel pressure guage and screw it on the schrader valve and drive the car around tillit happens again.
If it cavitates and the pressure is low then obviously the pump is defective or there is debris in the system or the rubber hose that connect the pump to thr line out has a pinhole.If the pressure is good then it is further on maybe injectors not pulsing as they should.
[This message has been edited by Boogaloo (edited 10-22-2010).]
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11:39 AM
josef644 Member
Posts: 6939 From: Dickinson, Texas USA Registered: Nov 2006
I noticed that there was just a bit if difference between the size if the two pump outlets when I installed a V6 pump in to my 88 4cy tank. Maybe this is the problem? From my thread, and I didn't use a pulsator, I used the piece of hose furnished with the new AC Delco pump.
There was just a little bit difference between the old 4 Cyl pump and the new AC Delco V6 pump
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05:53 PM
Nov 8th, 2010
jackcastro Member
Posts: 620 From: WESTON,FL,USA Registered: Dec 2005
To those of you who offered help, thank you very much. I thought I'd post the final solution to the problem, just in case someone else has the same problem. The issue was with the baffle, part of which broke loose. We emptied the tank and then found out the problem. I was keeping the tank almost full all the time because of this issue, and we could not see well inside the tank until we decided to drain it for inspection. Everything has been perfect ever since.
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08:49 PM
joshua riedl Member
Posts: 1426 From: watertown wi USA Registered: Jan 2004
I had this same problem. My tank was severely rusted and the baffle was sliding back and forth. I got a new tank from the junkyard and the pickup assembly was in better shape than mine. I did reuse my fuel pump and the noise has not returned. I don't know exactly what was causing it, I assumed it was the baffle moving around and blocking fuel. First I would look at the tank and see if it's damaged at all. The pickup sits pretty low to the tank and it could be getting blocked.
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08:55 PM
phonedawgz Member
Posts: 17104 From: Green Bay, WI USA Registered: Dec 2009
