Page 1 of 2 12 LastLast
Results 1 to 10 of 13

Thread: Adventures in Vapor Lock

  1. #1
    Join Date
    Apr 2021
    Location
    SF Bay Area
    Posts
    234

    Default Adventures in Vapor Lock

    Hello Rovers!

    I’ve been dancing around this problem for a year now - stalling, hard starting when hot, leaving me stuck at intersections in the left turn lane and the Series won’t start back up. I threw all kinds of parts at it: new Webber carburetor, new Pertronix distributor , new mechanical fuel pump. Worked okay for a time, and the symptoms returned! Some research into the problem, and it seems everyone with old cars is having this problem now - Vapor Lock - due to new gas additives like ethanol making the boiling point of gas much lower.

    Vapor Lock:
    The problem seems to be that ethanol in gas (E85, etc) lowered the boiling point of gas in the last 15 years or so. So, on low pressure (carburrated) systems, the gas sits in the lines until the float bowl empties and asks for more fuel. It literally boils and turns to a gaseous state in the lines or the bowl and your engine is starved.

    Fixes:
    There are a couple fixes, I guess. Either you shield/cool the lines and or carb. Or, run a recirculating fuel filter and electric fuel pump to constantly move hot gasoline in the line back into the cold fuel tank. Or, the nuclear option, get an after market fuel injection kit.

    My progress:
    I have my gripes about each method…so I started from the lowest one first. My gripes with each method:
    * Electric fuel pumps are loud. Without a ‘dead man’ switch, they just keep pumping gas if there’s voltage…so if you get in a crash, they just keep squiring fuel on your burning bones.
    * EFI systems are great. But I got a Series because I wanted a classic, mechanical, simple car. Am I gonna put a computer and extra wiring in now? Ugh!

    Heat profile:
    First thing first, I bought a temp gun to get temp readings in places. I wanted to see where in the engine bay is hot, so I could route the fuel line away. Here are some spot temperatures after a 20 minute warm up drive on a 65 degree California Fall day:

    * At fuel pump- 95-110 degrees
    * At head, near water spout, right side- 134 degrees
    * Top of head, near radiator line- 119 degrees
    * At head, left side- 118 degrees
    * At intake manifold, near head - 169.5 degrees
    * At exhaust manifold, halfway to carb - 272.5 degrees
    * At exhaust manifold, right at head - 360.7 degrees
    * At fuel bowl on carb - 87.8 degrees
    * At phenolic block on carb- 93.7 degrees

    So, with the standard routing of the fuel line from the fuel pump, across the front top of the engine and into the carb…we go from about 95 degrees to a solid 120 most of the run, and we pass into the carb over the intake/exhaust manifolds that go from 360 degrees to 167 in less than 10 inches. And this is with my hood up. Likely it stays hotter with the hood down.

    Boiling point of gas:
    I tried to find exact data, but it’s hard. Gas is blended with different additives at different times of the year. Also, they list “boiling point” in 3 numbers…where the first number is “5% of the gas is boiling”, the second is like “50% of the gas is boiling” and the last one is 100%. So the range they give is like 90 degrees to 300 degrees. Your numbers may vary. So, by my understanding, SOME boiling(5%?) is happening as low as 90 degrees at atmospheric pressure(inside the fuel bowl). The mechanical fuel pump is rated at around 4-6 PSI, so it might boil sooner(like a tea kettle under pressure boils water faster).

    So, I guess no wonder it starts Vapor Locking. I bet the fuel gets to about 120-150 and vaporizes.

    First attempt to fix:
    As I said, I wanted to try the least radical fixes first. So, I decided to route my fuel lines toward the outside of the engine bay, avoiding resting on the block. I also got some heat shielding sleeves for the fuel lines from DEI(DEI-010403) In addition, I got a small finned heat sink tube type oil cooler and put it in the front grill area, just in front of the radiator and ran the fuel line through it. So, the fuel line is shielded, and runs through 65 degree ambient temp around the outside of the engine bay and gets an additional cooling boost from the finned heat sink getting fresh air up front. As an aside, pipe fittings are a nightmare! There are a half dozen standards and good luck finding exact hardware. In my case, the oil cooler had a -6 AN fitting that needed to be reduced to -4 AN, then turned by a 90 degree bend, before outputting to 1/4” hose Barb. That was like $80 of fancy black anodized aluminum pipe hardware and 30 minutes on the phone with a tech to find all the right combos.


    Did it work?
    Well. Partially, but no. The Vapor Lock came back. Stalled twice. But, I noticed it cooled off very quickly at each stall. I usually had to wait 5-10 minutes to restart. Now, it was back to non-boiling temps in 30 seconds-1 minute. So, less desperate…I could restart in one light change. Whereas before, I was a scene blocking traffic for 3-4 traffic light cycles.

    Next steps:
    I may look into heat shielding over the intake manifold to block exhaust manifold heat. Might look goofy, but I just need like 10 degrees difference.

    But, ultimately, I think I might have to bite the bullet and do the recirculating lines and electric fuel pump. Does anyone have advice on tapping the fuel tank to take a return line? Is there a Land Rover part that works good? I don’t want to reinvent the car. I know later Defenders (EFI) and such have recirculating fuel systems. Any advise much appreciated!
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	6E5449B0-84E5-4324-93B8-EE6D660C5F10.jpg 
Views:	49 
Size:	86.3 KB 
ID:	14124   Click image for larger version. 

Name:	D49D50AD-3E09-4E47-BDC3-B96D79DC8538.jpg 
Views:	48 
Size:	101.3 KB 
ID:	14125  
    ...┌───────┬──,,
    ...|______OD__|__\\_____
    ...d ..__ .........° |°... | ..__....p
    »»└/ | \────┴──┴/ | \─┘≡
    ..../..@........................@

    1973 Series 3, 109

  2. #2

    Default

    I use ethanol free fuel. More expensive than premium and much more than regular grade, but my Landy isn't my daily driver, so it's not that big a deal. I also use ethanol free gas in the lawn mower and other small engine tools.

    After trying three or four new mechanical fuel pumps to cure a "running out of gas at high load / high RPMs" problem I installed an electric fuel pump in parallel to the mechanical one, with an on/off switch I can flick if the engine starts bucking.

    It gets pretty hot in Georgia, but the above has cured my Landy's vapor lock & fuel starvation woes.

  3. #3
    Join Date
    Jul 2020
    Location
    UK
    Posts
    247

    Default

    Land Rover went to a recirculatary system on the petrol 90/110 models with a mechanical lift pump, due to vapour locking, as the engine/carb is mounted higher in the engine bay than the Series vehicles . They also fitted a vapour trap (NRC9772) in the fuel line so that vapour was returned to the tank before the carb. They then later changed to a rear mounted electric pump and dispensed with the trap. They may have also fitted a crash sensor to immobilize the pump under crash conditions. On a Series you could use a Diesel fuel tank and its fitting for the return as a diesel has that as standard or drill another hole in a petrol tank & fit the diesel return pipe into that. Many aftermarket fuel tanks are supplies as diesel ones as standard (So it serves both with one tank) having a blanking plate on the reserve.

  4. #4
    Join Date
    Dec 2010
    Posts
    341

    Default

    If you have much rubber in there for fuel get rid of it as rubber absorbs and holds a lot of heat, I've no problem with my s388 vapor locking. mech pump, all else is OEM except the emissions stuff is gone. just a line from the pump to filter on the firewall to the carb.

  5. #5
    Join Date
    Sep 2010
    Location
    killingworth CT
    Posts
    832

    Default

    I like what you have done with the fuel lines, I have a series 2a, petrol, weber carb. I have noticed, does not like the hot start, but will cold start, Right Away. But, after replacing my distributor, with a Petronix unit every start is faster and cleaner, no long cranking anymore. I might ask what octane fuel are people running for a Turner motor?
    Cheers,

  6. #6

    Default

    I also have vapor lock problems on my 67 Series IIa. Its frustrating and I keep a bottle of water in the cab along with a cloth to wet and wrap around the carb. I am going to pass along some interesting advice I was given on the forum by Rover 03. Bob said he also had VL and believes he cured it by one or a combination of two methods. His first was to have the exhaust manifold ceramic coated and the second was to always use high test gas.
    Dave

  7. #7
    Join Date
    Apr 2021
    Location
    SF Bay Area
    Posts
    234

    Default

    [Update] Dag nabbit! I think Vapor Lock is the boogy man. After weeks of trying to sort it out, and all my local car guys looking at me like I’m crazy. I have some actionable info.

    I decided to buy the electric fuel pump + return line setup. Turns out the parts manual has the part to make it recycling. It’s just a pipe fitting with a 90 degree turn and a down spout into the fuel tank. The fuel tank is already fitted for it, it’s just blocked off on models that don’t use it. Great. So, as a good measure, I bought a $15 in line fuel pressure gauge, too.

    I put the fuel pressure gauge on the augmented system(before installing the electric pump and return line). It reads a perfect 4.5 psi. Great thing is, it’s pressurized even with the car off. So, essentially, it records the fuel pressure that it was at when the car turned off. I drove it and hit my mystery shut-off problem. Guess what? 4.5 psi!!

    All this work, and my fuel delivery is fine!

    I DID notice some electrical shenanigans. The car shut off mid 3 point turn, and my blinker also cut out. Hmm? 2 minutes of sitting, and the blinker comes back on. Guess what? Car starts right up. Turns out, this is 100% repeatable. Every time the car dies like this…if you try the blinker, no luck. As soon as the blinker works, you can start the car…which happens about 1 minute later.

    I’m not superstitious. And I’m also not too proud to look the fool if it helps someone else. So, I’ll admit, I jumped to the Vapor Lock band wagon…because it fit the description. Now, I’m thinking it’s electrical. You need 3 things: Air, Fuel & Spark. I assumed spark was fine, because it ran. It was getting spark SOME of the time!

    Now, I looked at the wiring diagram. There’s only 8 fuses, and lots of systems share those fuses. So, it seems silly the turn signal blinker would be on the same circuit as maybe the ignition coil. But, yup. All the electrical gremlins I had seemed to be on the same line. I had fuel gauge issues. It displayed right sometimes, other times it was dead. Water temp. All these things get ignition+ on the same circuit. So, my current thinking is I got a short or bad ground somewhere that gets a little hot and kills power to my ignition coil. No way to check without having someone in my engine bay while I drive…which isn’t going to happen.

    I put the electric fuel pump on the shelf and ordered a full wiring harness from AutoSparks in the UK. I’ve been putting off the rewire for a long time…living with dodgy wiring and fixing little shorts and grounds here and there. I’m sick of it. Going to do the full rewire. The kit I got has some extras, like Fog/Running lights circuits, radio circuits and auxiliary 12v dash circuits, too. So, it’s an upgrade I been meaning to do.

    So, it turns out the fuel line modifications were not needed. I might revert them. Or I might keep them as a “just in case” stop for possible Vapor Lock issues later. If I had to give advice, I’d say to buy the in line fuel gauge FIRST to rule the fuel system out. It was only $15 and easy to install, and would have saved me some trouble.

    Old cars, man!
    ...┌───────┬──,,
    ...|______OD__|__\\_____
    ...d ..__ .........° |°... | ..__....p
    »»└/ | \────┴──┴/ | \─┘≡
    ..../..@........................@

    1973 Series 3, 109

  8. #8
    Join Date
    Oct 2011
    Location
    Mountains of Western Pennsy.
    Posts
    588

    Default

    My truck is a little different from most Series Land Rovers. it's 1976 Series 3 109 HiCap one ton, with an early Range Rover drive train. Even with the inline 6 cyl it had an electric fuel pump made by Fascet, return line and and no mechanical fuel pump. It's now a 3.5 V-8 with a John Wolfe Racing intake (Offenhauser 360), Edelbrock 4bbl, Carter electric fuel pump, and a Pertronix ignition. So it's more like a Stage 1 with its LT95 gear box, Fairy overdrive, and Salisbury (Dana 60) rear diff. I've never had an issue with vapor lock, even on very long trips, and I can keep up with super highway traffic easily. One thing, I don't understand is why anyone would install an electric fuel pump and retain the mechanical one. Skip the mechanical pump and run the fuel lines away from the engines hot spots. In the old days of racing, some guys would run both and eventually blow the diaphragm in the mechanical pump and fill the engine with gasoline, sometimes with spectacular results. And... go to the pick-a-part and get an inertia switch out of just about anything and wire it into the electric fuel pump circuit, Safety First.

  9. #9
    Join Date
    Apr 2021
    Location
    SF Bay Area
    Posts
    234

    Default

    About mechanical and electrical fuel pumps on same line:
    I guess I read on some forum that it wasn’t a big deal because the mechanical pump had a diaphragm/valve that only went one way. So, the electrical just ‘helps” the mechanical in that setup. But, yeah, it seems redundant. I do like the rugged nature of the Series mechanical fuel pump. It has that sediment bowl to catch big rocks, and the priming handle to get some gas in the carb after sitting for 6 months. Very cool. I’m sentimental about removing it!

    Tell me more about this diaphragm failure thing. You mean it can leak gas into the crank case? Or overpower the float valve in the carb?
    ...┌───────┬──,,
    ...|______OD__|__\\_____
    ...d ..__ .........° |°... | ..__....p
    »»└/ | \────┴──┴/ | \─┘≡
    ..../..@........................@

    1973 Series 3, 109

  10. #10
    Join Date
    Oct 2011
    Location
    Mountains of Western Pennsy.
    Posts
    588

    Default

    If the diaphragm fails fuel is delivered to the crankcase. Nothing like washing down bearings with gasoline. If you use an electric pump then priming the carb isn't needed, and you can get the fuel line away from engine heat. High pump pressures can sink the carb float, an adjustable regulator solves the problem. Just don't use a high pressure (racing) electric fuel pumps.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
About us
Unparalleled product knowledge. Our mission is to support all original Land Rover models no longer supported by your local Land Rover franchise. We offer the entire range of Land Rover Genuine Parts direct from Land Rover UK, as well as publish North America's largest Land Rover publication, Rovers Magazine.
Join us