Heat cause relay failure?

hiram6 · Posted: Wed Jun 24, 2009 6:37 am Post subject: Heat cause relay failure?

Is heat a common cause or contributing factor for relay failure? My Westy died while sitting in Atlanta rush hour traffic yesterday, and I'm curious as to why it choose that moment (rush hour) and place (one of the busiest interstates in the area) to leave me sitting on the side of the road.

Unfortunately, this meant a flatbed tow home, since I wasn't in a place where I could safely do any kind of diagnosis or repair. So, once I got it home last night, I determined my fuel pump had stopped working.

(1) test light showed no 12V at pump
(2) quick test with a spare motorcycle battery showed the pump itself was fine
(3) swapped out the two fuel pump relays with spares, and it fired right up.

So, one of the two fuel pump relays failed while sitting in traffic on a hot as heck day. Is heat a contributing factor? If so, the why are these relays located in the engine compartment? Wouldn't it make sense to put them somewhere else. like maybe under the bench seat inside the van?
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1985 Westy, 1.9L automatic (Daisy)
1996 Mazda Miata
1998 Jeep Grand Cherokee 5.9 Limited

You can't lie around on the beach and drink rum all day.................unless you start first thing in the morning.

tencentlife · Posted: Wed Jun 24, 2009 8:35 am Post subject:

C'mon, you know heat is always a major factor. Old stuff (and even some new stuff ) is going to fail sometime; it'll probably do it when it gets hot.
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Dogpilot · Posted: Wed Jun 24, 2009 8:57 am Post subject:

Its not just the relay getting hot. I would also suspect the pump. It may be drawing a bit more current that it should. The relay is only rated for 20-30 amps (can't remember the exact number for a 53). As your pump ages it get less efficient, kind of like all the other electrics in the van. the Bosch pump uses fuel to cool itself. So if you are in the heat, which I understand is like 98° at the moment, and have hot fuel, old pump. You have a situation where the whole system is at its least efficient. Relay went first.

Now that you have a new relay in place, feel it after about 10 minutes of running, see if it is hot. Or, if you have the technology, measure the current. Unfortunately, most meters only go up to 10 amps.

BTW, I'll be in Carrollton next week, then its off to Oklahoma for an NTSB engine teardown, with a day or two trying some new trails. Home for a few days and then to Borneo for two weeks. Got to get that Twin Otter out of the jungle. Lifting it out with a CH-54. I'll have to post a pic of this.
_________________
Geology with a Syncro rocks!
86 Syncro Westy AKA "The Bughunter"
98 Disco I
08 Range Rover SC
08 VW Rabbit S
1951 O-1G

hiram6 · Posted: Wed Jun 24, 2009 9:08 am Post subject:

Okay, I kinda suspected as much. The heat, along with an old pump, did me in.

My shameface is because I know I'm partially responsible for the failure. I still have cavitation whining at my pump, so for many months my pump has been straining and working harder than it should. AND, at the same time, I suspect the cavitated (new word?) fuel has not been cooling the pump as well as it should.

I really need to plumb the return line across into a tee between the tank and the pump. Looks like I need to buy some fuel line and a barbed tee. I have some of the correct fuel line clamps left over from a previous project.

Oh joy, I'll smell like gasoline for the rest of the day. Laughing

_________________
1985 Westy, 1.9L automatic (Daisy)
1996 Mazda Miata
1998 Jeep Grand Cherokee 5.9 Limited

You can't lie around on the beach and drink rum all day.................unless you start first thing in the morning.

tschroeder0 · Posted: Wed Jun 24, 2009 9:21 am Post subject:

on the subject of cavitation (ie noisy pump) I have never had to add an extra line to any van I have ever had or worked on, when the pump has benn noisy it has almost always been a filter that is getting plugged or in one case a piece of junk in my tank occluding the outlet at times. I guess what I'm questioning is why you would have to add anything to such a simple pumping system, it seems overcomplicated? Just my thoughts, Todd

hiram6 · Posted: Wed Jun 24, 2009 10:02 am Post subject:

tschroeder0 · Posted: Wed Jun 24, 2009 10:03 am Post subject:

Hey, thanks that explains a lot, good new info (for me) Good luck!

Vanagon Nut · Posted: Wed Jun 24, 2009 10:43 am Post subject: Re: Heat cause relay failure?

GrindGarage · Posted: Wed Jun 24, 2009 12:53 pm Post subject:

I thought old people like the heat thats why they move to Florida.
_________________
-cliff

91 Vanagon AUTO
97 Single Port EJ22 all smallcar.com

anthonywesty · Posted: Wed Jun 24, 2009 4:12 pm Post subject:

A few years ago my vanagon 84' with the engine cold start fine but in a long trips and the engine hot ,when I turn off the engine and tried to start again don't start up and waiting 15 min. and the engine start up without problems. I replaced the fuel pump relay and today the van start fine and no more start up problems.
_________________
82' Westfalia 2.0 16V with Digifant.
86' Vanagon GL
http://i223.photobucket.com/albums/dd147/WestyBOYPR/westfaliaCY.jpg


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