Collapsing fuel pickup hose. Truth or fiction.

[Citizen]

A quick summary of my problem:

The engine quits while driving. Takes a while to start happening, but once the engine does quit the first time, it usually takes 10-15 minutes before it will restart. Then it will run form 3-10 minutes before it quits again. This cycle repeats itself over and over again.

My theory was that the gas is getting too hot and the fuel pickup hose is collapsing inside the tank, thus cutting off fuel to the engine. Letting the car cool down for 10-15 minutes, or adding fresh gas (if the tank is not already near full) seems to get me going again. This is a problem I’ve heard or read about on this forum a number of times.

To solve this, I want to affix the fuel baffle directly under the fuel pump, and thereby shorten the pickup hose so it is straight, and has no curves where the hose could kink. I also wanted do the old screen-door-spring trick, just to insure the hose cannot collapse when it gets hot. I could also use my friend Shannon’s suggestion of putting insulation around the coolant line that runs near the gas tank.

All that said, today I ran some tests. While in my garage, I ran the engine a good 20 minutes, so to get to normal operating temperature. Temp gauge reads normal (see exhibit 1), and the electric fans cycle on/off as they should. Side note: I cannot make the engine quit while running in my garage (doesn’t get hot enough, I think).

Anyway, I decided to measure the temperature of the fuel. As hot as I could get the car (in my garage), the temperature only measured 92F (see exhibit 2; picture quality is poor, but I was able to read the temperatures acurately). I also measured the engine coolant temperature, which was 184F (exhibit 3). Both measurements were made within 2 minutes after engine shutdown, so these temps should have been pretty close to actual temperatures when the car was running at its hottest temperature. I also repeated the measurements a few minutes later, and although both fuel and coolant had dropped a few degrees, I still confirmed that the engine had reached normal operating temperature, and yet the fuel got no higher than 92. Outside (or ambient temperature inside my garage) was around 86F.

These measurements leaves me to reconsider that my engine quitting problem while driving might be due to high fuel temperature, which in turn leads to a collapsed pickup hose.

How could the hose collapse at only 92 degrees? Visual inspection of the hose itself still inside the tank showed no obvious problems.

Anyone have any thoughts or suggestions for me?

I also plan to replace the coil, and have a good look at the RPM relay contact points.

Thanks in advance.

[82DMC12]

Have you ever replaced the pickup hose? The design is ok, but when the hose gets old, it gets soft, and can collapse. If you don't know how long since it was replaced, you should change it with a new one and go for a drive.

Andy

[Citizen]

Have you ever replaced the pickup hose? The design is ok, but when the hose gets old, it gets soft, and can collapse. If you don't know how long since it was replaced, you should change it with a new one and go for a drive.

Andy

Thanks Andy.

I hose is new as of 2005. Is that old enough to replace even if it all "looks" good inside the tank?

Thomas

PS. One more thing....I noticed the baffle is not totally secured inside the tank. It slides around easily at the bottom of the tank. Is that normal?

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[sdg3205]

If you shorten the hose to the hervey baffle style you wont need a spring.

Try the spring but my money is on the coil. Do you have an original Bosch unit? I had the exact same issues and did Everything possible to the fuel system only to learn the coil was toast.

Change your coil. It's like 36 bucks and you plan on doing it anyway.

[Citizen]

Try the spring but my money is on the coil. Do you have an original Bosch unit? I had the exact same issues and did Everything possible to the fuel system only to learn the coil was toast.

Change your coil. It's like 36 bucks and you plan on doing it anyway.

Yes, the coil is a blue Bosch, and it looks old. I asked at a local auto parts store and they said coils generally don't go bad like that (intermitently).

And yes, I was going to replace the coil anyway, just cause it's so old. Anyone have a cross-reference?

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[dmc6960]

Thanks Andy.

I hose is new as of 2005. Is that old enough to replace even if it all "looks" good inside the tank?

Thomas

PS. One more thing....I noticed the baffle is not totally secured inside the tank. It slides around easily at the bottom of the tank. Is that normal?

...

Truth.

2005 should be new enough to have one of the higher quality hoses, unsure if the materials makeup has changed after that. When exposed to both gas and heat, even the newer ones get softer, just not as soft as the old ones. Because of the complex design of the pickup hose, if it is not installed 100% perfect, heat and gas could still cause it to collapse. Think of it as a slight kink which gets more kinky as it softens. Other factors which can attribute are the condition of the pickup screen. If its even mildly plugged then suddenly there is a larger vacuum force on the pickup hose as the gas is sucked through it. There can also be fuel pumps which respond negatively to the heat without any other factors. There was a string of low quality pumps that made it through DMC distributors at one point in the 2000's, perhaps you ended up with one of those.

The baffle is supposed to be secured to the tank via a single stud and two wire clamps. On some cars this stud has rusted or broken off therefore it is very difficult to keep a secured stock setup and many opt to install an under-pump setup. I however am one of those people who believe in the stock baffle/pickup setup entirely. Yes, I know there are weaknesses but only if not done 100%. Until DMC's new integrated fuel pump is available, no other pickup/baffle setup gives the low gas performance necessary for the vehicle. I know others will argue against that point but I'll just be a donkey to those and not listen.

In 2010, I was caravaning with one other person to/from DCS. His car developed the hot-gas-collapsing-fuel-pickup syndrome. Got so bad at some points that the engine would no longer run at a higher load than idle. Fix EVERY time was a refill with cold gas. After getting home that person replaced the pickup line, of unknown history before his recent ownership, and never had the problem again.

[Citizen]

Wow! Andy, Dave and Jim. Thanks for all that good info!

Here's what I'll do:

1-Replace the pickup hose, not matter what it looks like now.
2-Try to secure the baffle to the bottom of the tank better (it's secured only on one side).
3-Replace the coil.
4-Check/clean contacts on pump and RPM relay.

Thanks again guys!

Thomas

[82DMC12]

It's really important that the baffle and support wires are installed correctly. If not secured to the tank floor they might even be floating around in there! Dicey to be sure. I would empty the tank out and give all those parts a thorough inspection. The pump screen is inexpensive - change that too if at all suspect. You should find the frying pan shaped baffle, the baffle bottom cover, two shaped wires to hold the baffle down, a really curvy pickup hose going through the pan into the center of it with a screen on the end shaped like a hockey puck. It's all held down by a 10 mm nut and a washer. The return hose should be clipped to the frying pan and directed over the screen.

If anything is missing, you will need to get the part and make it right. Sounds like classic suction problem to me.

Andy

[nkemp]

I had similar problem. Would idle fine but would kill going forward. Funny thing was that it would run fine in reverse (but a bit hard to drive :-).

Turns out that the tank stud holding the sump/baffle was broken and the PO had added a lead weight to the pickup line. When going forward the line would get pulled back and kink. In reverse it would pull the other direction and extend the hose and it would run fine. At idle you don't use enough fuel to cause a problem.

FYI,
Nick

[Bitsyncmaster]

As many have found out during a pump replacement on the road.....The gas in the tank gets very hot. I did some testing also and found my pump would start to buzz when the gas in the tank got above 125 deg.F.

I had installed the spring in the pickup hose and it never stopped the buzzing pump. I'm not saying the hose can't collapse but I think it's not as common as most think.

I think the tank heats with the returned gas. I ran tests and the return gas was always about 2 deg F hotter than the supply line. So it's a time dependent thing to get the gas to heat up.

I had a post in the old forum of my solution (still need to do a long drive). I made a cooler for the return fuel which is wrapped around the AC accumulator.

[DavidProehl]

Truth.
In 2010, I was caravaning with one other person to/from DCS. His car developed the hot-gas-collapsing-fuel-pickup syndrome. Got so bad at some points that the engine would no longer run at a higher load than idle. Fix EVERY time was a refill with cold gas. After getting home that person replaced the pickup line, of unknown history before his recent ownership, and never had the problem again.

That was me. Jim helped me get home on that bad pickup line and an original vinyl clutch line. Both have since been replaced. One slight correction to the above: after replacing my hose I still had the issue, just less often. I then installed the spring and now I've never had an issue. Even driving more than 100 miles on a sunny 90 degree day. Install the spring. It is a pain to do, but it works and you won't wonder if your hose is collapsing on you.

[David T]

The soft pick-up hose syndrome appears most acute in warm to hot weather and a fuel tank less than 1/2 full. It is VERY important that when the fuel pump is installed you take care to not twist the hose which can lead to it kinking. The fuel pump creates a LOT of suction on that hose so if it is soft it can collapse. Besides having a stiff hose you can install a spring inside to prevent it from collapsing. As pointed out, ALL of the parts in the fuel tank must be kept in good condition and properly installed.
David Teitelbaum



QUOTE=DavidProehl;53134]That was me. Jim helped me get home on that bad pickup line and an original vinyl clutch line. Both have since been replaced. One slight correction to the above: after replacing my hose I still had the issue, just less often. I then installed the spring and now I've never had an issue. Even driving more than 100 miles on a sunny 90 degree day. Install the spring. It is a pain to do, but it works and you won't wonder if your hose is collapsing on you.[/QUOTE]

[Ron]

I'm with Jim and the donkeys ;-)


Sorry if I missed it, but why exactly do you think it is running out of fuel? Can it be something else heating up/breaking down...? The plate doesn't have pressure during the 10-15 minutes? or?(?Filter or strainer packing up?)
Just wondering...

[Citizen]

I'm with Jim and the donkeys ;-)


Sorry if I missed it, but why exactly do you think it is running out of fuel? Can it be something else heating up/breaking down...? The plate doesn't have pressure during the 10-15 minutes? or?(?Filter or strainer packing up?)
Just wondering...

I think it was running out of fuel because the engine quits while I'm driving. Yes, something else could be over heating, or it could be a blockage other than a kinking pickup hose. I did notice the RPM relay got extremely hot. I will also be replacing the fuel pump screen as well.

Thomas

[Ron]

That be the case... you might want to pull the coil wire and see if it will jump to any ground and that the air plate has the same resistance as when it isn't giving a problem first...

[Citizen]

Hey everyone,

I think I’ve finally proven the collapsing fuel line theory (the fuel line inside the tank, when the fuel gets too hot). But first a little background:

I’ve started having fuel starvation problems with almost no warning. My DeLorean would quit after it warmed up, either driving or just while running in my garage. Previous to this, the car had been starting just fine, hot or cold. But then out of the blue, it started dying after it got hot

So I replaced the 02 sensor, and then had the accumulator replaced as well. Still, the car would quit when it got hot enough, and wouldn’t start for 10-15 minutes, or after adding cold gas to the tank. So I suspected I was experiencing the old collapsing fuel line problem. I had always believed it was just a myth, or at best, just a theory.

Now I think I’ve proved it. This evening I removed the fuel pump and found two problems.

First, the rubber casing around the fuel pump had somehow partially melted (see photo). And there were collections of this thick, black, sticky, melted stuff at the bottom of the gas tank. It looked like the BP oil spill in the gulf. It was something like a very thick molasses, and it stuck to everything it touched. I got it on my hands while cleaning the inside of the tank and it barely came off using straight gasoline as a hand cleaner. Even then, it took lots of soap and scrubbing afterwards. I still don’t have it all off as I write this. I wanted to take a picture of my hands, but I didn’t want to touch my camera with this stuff on my hands. Now I think I know what POR-15 is made out of.

Anyway, my neighbor thinks the rubber is breaking down due to the ethanol our brilliant government requires to be put in the gas we buy (it’s up to 10% here in Texas). The fuel pump and all its components are only 7 years old, so would it be common for the rubber fuel pump boot, lines, etc. to start melting or chemically breaking down that soon?

Anyway, secondly, when I removed the pump, I noticed the fuel pick-up hose was partially collapsed, even cold (I hadn’t run the car in two days, and the ambient temperature was about 75F). See photo, red arrow. So when the gas gets really hot, the hose must be totally collapsing. On a side note, notice how the banjo is warped (blue arrow). The plastic seems to be breaking down as well. Further evidence of the effect of ethanol? I wonder.

So now, I think I’m going to bite-the-bullet, and buy the new style fuel pump when I can get my hands on one, and install it, and be done with this mess. And I’m still going to replace the coil just to be safe, as it looks like the original blue Bosch one.

More to come. Please chime in if you have experienced something similar to what I’ve described.

Thomas

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[DMCMW Dave]

Anyway, my neighbor thinks the rubber is breaking down due to the ethanol our brilliant government requires to be put in the gas we buy (it’s up to 10% here in Texas). The fuel pump and all its components are only 7 years old, so would it be common for the rubber fuel pump boot, lines, etc. to start melting or chemically breaking down that soon?

Thomas

...

Pretty common. I agree that modern gasoline is really messing things up. The wierd thing is that the rubber boots hold up pretty well if you drive the car enough that the fuel never gets stale (as short as 6 months), but sitting for long periods of time the gas apparently changes chemistry and attacks the rubber. You normaly don't see this level of deterioration in that short of time in a car that is driven routinely.

What is the driving vs storage history over that 7 years?

[Citizen]

What is the driving vs storage history over that 7 years?

The first few years, I was able to drive it a fair amount, no less than once per week. Even a few long trips. But in the last few years, I could barely drive it much on the road, but could only run the engine while in my garage, no long trips. Never let more than a week go by without running it.

[Bitsyncmaster]

Your fuel in the tank probably will never get as hot just idling in your garage. It normally takes a few hours of driving > 90 degree heat to get the common pump buzz.

Not saying your problem was not the pickup hose but I still don't think a good pickup hose is the cause of pump buzz.

[Citizen]

Your fuel in the tank probably will never get as hot just idling in your garage. It normally takes a few hours of driving > 90 degree heat to get the common pump buzz.

Not saying your problem was not the pickup hose but I still don't think a good pickup hose is the cause of pump buzz.

Roger that, for sure. But my problem never was a buzzing pump. It was more fuel starvation while driving (or while idling in my garage). I'm leaning towards the collapesed hose theory because when I pulled the old one out (cold), it was already collapesed (see picture in previous post).

Thanks for all the responses though, Dave and Dave, and David, and David T, and Ron, and all others!

Thomas

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[Bitsyncmaster]

My thinking is....if your hose starts to collapse, it should continue to collapse until all fuel is shut off. So the engine should die. Many people attribute the buzzing fuel pump to a collapsing hose.

[David T]

It isn't just collapsing, because of the shape of the hose it is also prone to kinking. Especially if the hose is old or soft. Add to that some tension on it because the fuel pump is twisting it a little. Add a little heat and it can kink right up. The fuel pump moves a considerable amount of fuel. To do that it has to suck hard and with a soft hose it doesn't take much to kink or collapse it. That's why I recommend a spring inside the hose.
David Teitelbaum




My thinking is....if your hose starts to collapse, it should continue to collapse until all fuel is shut off. So the engine should die. Many people attribute the buzzing fuel pump to a collapsing hose.