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| Fuel Starvation/Vapor Lock? '84 Regal P-30 | Login now/Join our community |
Had a problem this weekend on first spring trip of 150 miles each way. New plugs, wires, rotor. Have always used fuel stablizer. After about one hour of 3500 rpm interstate travel, engine starts to miss and seems like a fuel starvation problem, (no backfiring or bad engine noise, just intermitent hesitation). This happened going and coming. The driving temps were in the low 60's both ways, I recently serviced cooling system and the engine running temp was well within SOP. I could find no areas where fuel lines were in close contact to high heat sources, except a fuel pump mounted to the block and very close to front Torley header pipe. If I let off the gas pedal and resumed speed, it would smooth out and run fine for about 10 miles and do it again. At each incident I would let off the gas, then re-accelerate for another few miles of smooth running. I searched the archives and found items to ponder. I just crawled out from under and in, looking for fuel filters and pump locations. I located the filter on the carb and one ahead of the front tank and will replace those. There is a fuel pump in the normal location for a mechanical pump. I can see the fuel lines going and coming from it but no electrical connections. It doesn't look like a mechanical pump, looks sorta like a brass colored oil filter about 3" in dia. with 3 small hose connections on bottom. I haven't been able to find any other type of fuel pump but records indicate a 12v fuel pump was purchased in 1999 (about 15,000 miles ago). Looked like the owner must have installed it as it was just a cash parts invoice with indiscript nomenclature and could have been for the genset, I suppose. Bottom line is it takes an hour of cool running at 3500 RPM's for the problem to start. I ran in really hot weather last year and never experienced this problem which seems to be heat aggravated. BTW: I also disconnected the cruise control even though it was finally working good, but this is not the problem either. Also, when I replace the rotor, it looked scorched. I also found a new spare distributor modulator in the locker but haven't installed it yet. Could it maybe be the problem? Sorry to be so long winded but want to give the best info I could for your consideration. Thanks some more, Don | |||
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| The Old Man and No Barth |
Sounds like the symptoms I had within a few months of bringing the rig home. I changed out all the fuel filters, and have had no problem since. Your rotor tip will look scorched soon after it is installed, but it would be unusual for the plastic to be scorchedl. I've never encountered that problem. | |||
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But Roy, If the filters were bad, why in both cases would it take almost an hour of running before symptom developed? I'm still wonder what type of fuel pump I have, electrical, mechanical or both. I've changed out mechanical fuel pumps on Chevy 350's before but this pump looks nothing like I've seen and suspect it is electrical mounted in the same location that a mechanical pump would be (but I see no wiring in this tight spot). And, since it is so close to header heat, I'm wondering if it is going south after getting hot? Where are most electrical fuel pumps located on 83-84 Chevy 454/P-30 Barth Regals? The plastic was scorched in the center of the rotor, inside and out. Guess I'll stick that new modulator in just for process of elimination. Those that have had them ((early 80's barth), please tell me what your electric fuel pump looks like and where it is located. I hope to find this gremlin quickly so that I can hit the road again this coming weekend. Thanks again. don | ||||
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| 1st month member |
I had the same problem, but it was an electric fuel pump. Mine is located on the frame next to the fuel tank. I even bought a inline fuel pressure gauge from Summit Racing to check it. ------------------ Eddie Chevalier '85 Barth Regal 28' P-30 454 '91 Honda Accord/'87 Yamaha YSR 50 Toads | |||
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| "First Year of Inception" Membership Club |
My 1983 25ft has two tanks and a electric fuel pump on the frame next two the forward tank. This pump feeds the mech pump on engine. The electric pump is wired thru a oil pressure switch, in case of accident it will shut down. Lost the power to this pump once and the engine would not run on the rear tank and barely run on the front tank. | |||
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Thanks fellows, I'll look again and see if I find an elect fuel pump close to tanks but I don't think its there, just a filter. How large or small would the typical electrical pump be? Would a bad mechanical fuel pump, located close to a high heat source, deliver the same symtoms as a faulty electrical pump? And again, if this is a mechanical pump located where a mechanical pump usually goes on a GM motor, it sure doesn't look like any I've seen. Thanks again, don | ||||
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First Month Member 11/13 |
I'm with Eddie on the fuel pressure gage. It is the only way to know for sure. I would also heat shield the fuel pump from the header heat. Or even remove it if you have an electric pump near the tank. I run my Barth without an engine driven pump. The electric pump above the tank does it all. | |||
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I'm still trying to get a handle on what kind of fuel pump I have, located in the normal location of a conventional mechanical pump. As I mentioned, this thing looks like a simple cylindrical brass can (apprx 3"dia x 3" tall)with three small hose connections on the bottom. Repeat, it does not look like a conventional GM pump that I am familiar with, ie GM 350ci. I will definitly go with a new elect pump near the fuel tank but need to know what kind (make-part#), and wheather or not to run it through the mechanical(?) pump location or bypass it. What does the body of the conventional mech fuel pump look like? This one appears to be unconventional but I see no electrical connections. From your post and the archives, this definitly appears to be a heat sensitive, vapor lock, fuel problem, common with elect pumps, too close to high heat. Thanks, Don | ||||
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What you may be looking at is a canister that is used as part of the fuel return system. I have seen these on my 1981 Barth as well as on my Jeep. It appears that it returns excess fuel to the tank rather than building up pressure in the fuel bowls of your carbureter. If this is the case, it is usually placed close to the carb. In this location you can reduce the length of some of the hoses and reroute them away from heat sources. Barry | ||||
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Let me try this again. I have had the same problem on a 78 24' with a 454 chevy engine. Mine would work on one tank and not the other. I thought vapor lock all the time, but when had my "so called vapor lock" with outside temp of 22 degrees, started to look for a commom fuel filter. Which I found and changed and problem ended. the reason one tank would still deliver fuel was the heat and pressure build up in drivers side tank from muffler being installed to close to tank. Have installed heat shield between tank and muffler. Had to change fuel filters again last week as motor started running lean and losing power, would back off as you described and fuel would enough at lower rpms. Changed filters and just completed a 350 mile trip with no engine problem. Good Luck | ||||
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Barry, your info fits. Now I need to know if I should bypass it, installing an electric pump near tank fuel filter or replace the mech pump and run the elect pump supplied fuel through it? If I bypass it all together, do I just plug the fuel inlets and outlets and leave it attached to the block? Also, I still need advice on which electrical pump to install and where best to splice into power source. BTW: the fuel filter at gas tank was filthy but the one on the quadrajet looked fine, but will be replaced also. I've been hashing this over with the previous owner and I, like him, thought that a mechanical pump would go completely bad with nothing in between. This may turn out as simple as a dirty filter but I have doubts and would feel much more secure with an electrical pusher pump plus the mechanical. Mr Rabbit: Thanks also. You had me puzzled for a moment. Thanks all, I'm on it. don [This message has been edited by dogill (edited April 11, 2005).] | ||||
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| First Month Member 11/13 |
The evap canister on my 84 is black plastic and is not mounted on the block. It is mounted on the chassis to the right of the engine, and is much larger than 3 in dia. Rather, about 9 in dia X 11in tall. Back to the fuel pressure gage: A temporary setup can be made with a vacuum gage and flex hole. Most vacuum gages are also fuel pressure gages. Do you have an electric pump back there? Mine is a Carter rotary located right above the tank. It can be heard when the ignition is turned on. It feeds my 502 just fine. I used another carter on a rump rump boat with a fuel guzzling 468 in it. | |||
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Bill, I don't believe I have an elect pump above tank but that will be easy enough to verify, shortly. After a trip to the parts house, I can verify that I have a atandard mechanical fuel pump for this model 454, mounted to the block. I went ahead and purchased a 5 to 9 psi elect. pump. The instructions tell me its a bad idea to run the elect pump thru a bad mechanical pump as it could inject fuel into the crankcase. So this brings up another important question for stupo's like me. What do I do with the excess fuel return line at the mech pump? Just loop it or cut and plug at the source? Next question - would power source for new elect pump be okay to come from starter or closest solenoid? And finally, what about installing a new mech pump in addition to the elect, for redundancy sake? THX, don | ||||
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| 6/12 Formally known as "Humbojb"  |
I had a similar problem on a 460 Ford engine in a class c motor home. Fuel pumps and filters are always good place to look. But in my case, it was none of the above. The catalytic coverter had rusted from the inside, part broken off and the converter completely stopped up. The thing wouldn't run at all. Solution? Disconnect the converter, ream it out with a rebar, put converter back on and presto--the stinky old Ford ran. In fact it ran so good it's now in Sarrasota with a new owner. | |||
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