1960 Cadillac - Vapor Locking? FIXED

Specific repair issues for all GM cars + FWD vans
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liljoe
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1960 Cadillac - Vapor Locking? FIXED

Post by liljoe »

Hey, need some advise from some of the more seasoned then me out here. I have this car in my shop: http://forums.cadillaclasalleclub.org/i ... c=104893.0 and it is having a vapor lock issue. The fuel pump on these is mounted on top of the engine and has to pull fuel uphill about 18 inches. On hot days the car will run out of gas and will be pumping "air bubbles" in the glass separator bowel. To me this says it is vapor locking due to fuel getting too hot. The fuel line ( metal ) runs less then 6 inches from the exhaust in places, I am thinking that if I use some high temp braiding like you use on plug wires when they have to run close to header pipes to runt he steel lines through this should help keep the fuel from getting so hot. I checked the tank and lines for restrictions even though they are all new and found nothing wrong. If he is able to find 100% gas instead of the e90 that is at the stations in our area now it does somewhat better. My thoughts are that due to the lower boiling point of ethanol the original 1960 design will not function in 2016? Any input from those well versed in vapor locking will be appreciated, I have not had to deal with that issue due to fuel pumps being tank mounted now......
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Re: Cadilac vapor locking

Post by steven kiser »

I really don't think that Vapor Lock will cause pump to push "Air Bubbles" into the bowl. It's possible but I would remove gas cap and see if it's relieved. Vapor lock is a vent restriction causing a vacuum to form in the tank holding back the flow. I'm just talking out loud to help me hack through the vines and weeds that have taken over much of my long term memory. Six inches away should be plenty of room to keep the fuel in the lines from vaporizing. I am starting to clear up a bit so here goes. The first thing I would do is to replace any and all rubber (can't spell the proper name :shock: ) fuel lines and clamps, remove the gas cap, clear the area behind it, blow air through the fuel line trying to blow the "sock" off of the end of the intake tube. These socks would get partially clogged and cause a restriction after the engine has been running for a while. I would probably suggest to the customer that the tank needs to be completely and thoroughly cleaned out. Probably a good amount of silt has collected in tank. If customer refuses then I would at least install an in line fuel filter to catch the crap that will now flow without any restriction. I would tell customer that you would like to replace the new filter after the car has been driven around for a while. If after all this air bubbles still appear in the glass bowl I would check and see if the engine breather system is somehow restricted causing a build up of pressure in the crank case. This may blow through a weak fuel pump diaphragm causing bubbles. Either way I would suspect a faulty fuel pump diaphragm. Only reason I mentioned the crank case pressure is I didn't want to overlook it as the primary reason the pump failed. I remember fuel pumps failing many ways and ran into a fair share that would cause a power issue after the vehicle had been driven a while. As far as I know there is no real test it's a matter of testing and eliminating everything else. Back then it really wasn't a costly process to work back to the pump by eliminating everything before it. I really mean giving the area around and behind the fuel fill when you blow air through trying to blow sock off. Many times I've felt pressure building up as I apply more and more and when that sock blows off all that pressure will blow a stream or a broad spray covering a large area. I found you just can't Pansy around with the air. You may think the sock is off but you need to hear a gurgling sound in the tank that makes you think it's going to puke, not a little bubbling sound. I used a long rubber line clamped on the blow gun and fuel feed on the sender. I would no matter what unless a major issue developed work the blow gun into full open within about 10 seconds and using a pair of needle nosed pliers squeezed the line to see if there was no pressure build up in it. It should just be bubbling and banging away and possibly puking out the fill. Ya I know I'm stretching the answer way out but it's all I can do right now. Have a great weekend and good luck.
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Re: Cadilac vapor locking

Post by Tim Martin »

Having grown up in my Dad's garage in the sixties and seventies, I am inclined to agree with Steve's comments. While the term 'vapor lock' was a term we used back in that era of time to describe what seemed to be the boiling of fuel in the lines, there was perhaps a few vehicles and times when this would actually happen. However, I think there was more times when the main issue was not vapor lock but rather other issues such as a nonvented gas cap, or a leaking fuel line. Your idea of E90 having a lower boiling point than regular gas did years ago is legit however my thinking, like Steve's, is that there may actually be another issue. To address your interest in wrapping the fuel line, there is some wrap we use on exhaust tubes in some applications that are great heat barriers. Do not know the name of the stuff though, we use it so seldom.
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Re: Cadilac vapor locking

Post by nickscarcare »

I forget what it was made out of, but there used to be a little spacer that you could install below the carb, it was ceramic, or something like that, it helped as a heat sync to keep the carb cool so fuel would not boil in the bowl. I know they worked with pretty good sucess! If I think of exactly what they were called, I will let you know.
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Re: Cadilac vapor locking

Post by liljoe »

The tank, sender and all lines are all new. Pulled tank just to inspect ans sock is pristeen witn no restriction. For testing for a restriction or venting problem, I hooked up an electric pump and was able to pump 20 gallons on gas in about 10 mins and had no restriction on the line. When it messes up, you can unhook line out of pump and all that is comming out is fuel vapor. I have ordered protect-a-s;eeve from DEI corp. Gonna wrap fuel line in it and see what happens. The fuel pump is new also, he also tried one off a 59 he has that has no issues. The tank has a vent line comming out of it that is 1/2" i diameter and it is open to atmoshpere so that also helps me eleminate suction problem in tank.
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Re: Cadilac vapor locking

Post by brianp87 »

Id put an in line electric and be done with it.
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Re: Cadilac vapor locking

Post by Tim Martin »

brianp87 wrote:Id put an in line electric and be done with it.
Yeah. you could do that.
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Re: Cadilac vapor locking

Post by steven kiser »

When it messes up, you can unhook line out of pump and all that is comming out is fuel vapor.

Is the line coming from the tank to the pump the correct diameter? I have run into issues where someone had used an incorrect line size and the liquid couldn't fill it completely causing vapor pockets. The system on the vehicle is the good old pull and push system and even a minor wicked small hole can allow a minimal amount of air into the line causing all sorts of issues. Can't remember but is there a return hose from the pump to the tank? If so and the pump isn't making a full cycle it may allow a hiccup that is the starting point of this issue. Is the pump making a full cycle? I've seen internal engine issues that caused pump issues. Again I'm sorry if I can't be more precise but there was an engine out there that relied on an eccentric wheel off of the timing gear to run the pump. The lock ear for the wheel would wear off or break allowing the wheel to free wheel. Pump would work but at a bare minimum and would get hot as a, well I'll leave it up to the reader to fill in the phrase that suits them :lol:. We would remove the pump and check it's function and reach into the pump mount with a piece of steel rod that had a hose slid over the end and see if the wheel was spinning. Another thing I would on occasion run into was the pump arm being about an inch or two short at the very end that wouldn't give the pump itself a full cycle. I remember Airtex matching the OEM # as their part number and that helped me a few times. Some manufacturers will sell a pump that is one where the arm is a little shorter than one and a bit longer than the other for both applications. If there is any wear at all on the wheel the universal pump will not work. If you were the one that replaced the original pump had the running pad on the end worn off allowing the arm levers to cut into the wheel? Just thinking out loud right now. When the line from the tank to the pump was replaced did the tech install it on a different path because it seemed easier or anything for any reason the line not installed in the exact way the original one was? If so it may be causing the pump to strain and overwork and this will cause a vaporizing situation. Seen it before Sept 10th 2009 and Farmers paid for it :lol: :lol: Good Luck and don't overlook anything, remember vehicles of this era can't be compared to todays even in the smallest way. The trunk in this Cady is for holding things as you travel like cloths etc. Todays vehicles the trunk usually is a mounting area for light amplifiers, Audio and Visual Modules, pumps for suspension adjustments, Nitro Bottles, and a few other odds and ends. :lol: :lol:
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Re: Cadillac Vapor Locking?

Post by liljoe »

Well, I guess I can call this one fixed. He just called and he returned from a road trip down to the gulf and had no problems at all with it. I used a wire/hose wrap from DEI over all metal parts of the fuel line along with some gentle rerouting of the line and this seems to have corrected the problem.
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Re: 1960 Cadillac - Vapor Locking?

Post by steven kiser »

Congrats.
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