Cooler fuel with a return fuel system

Jezza

Jezza

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We have been working on a customer's TJ in the shop recently that was having some hard start issues when hot. We did all the typical recommended mods for dealing with under hood heat like the DEI heatshield and fuel rail wrap kit. We also wrapped the header and Y pipe with heat wrap as well as a hood louver kit. It was still having some chugging and sluggishness after a hot restart. I put some thermocouples under the hood near and on the fuel rail and the results were shocking. After a 30 minute drive and left to sit for another 30 minutes the fuel rail was approaching almost 300 degrees. When we restarted the engine it would slowly drop back to 175 or so. As a test we brazed some fittings on the stock fuel rail and rigged up a return line going from the rail back to the tank. The fuel temperature dropped almost instantly to ambient temperature. Driving the Jeep again for 30 minutes and hot soaking for another 30 minutes the rail was again almost 300 degrees, but the moment the key was cycled the temperature dropped almost 100 degrees. The hot restart issue was gone and the engine ran smoothly. Moving forward with this solution we designed a regulator assembly and fuel rail to be a return style system without brazed and modified parts. The regulator block is a direct replacement for the OEM unit and uses a Bosch 3 BAR regulator unit inside it. The fuel rail is bolt on as well. We did have to run a new fuel line from the back of the rail to the tank as a return. That was really the only custom work that had to be done. Everything else is bolt on. I did make a few extras and they are on our new website dedicated solely to Jeep parts.


https://texasjeepproducts.com/products/jeep-wrangler-fuel-pump-replacement-regulator-with-return

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That totally makes sense.

I wonder why my ‘98 doesn’t have a similar issue when it’s 115+ degrees here in Phoenix.
Do ‘98s already have a fuel return, or is there something drastically different between years?
What year was your customers Jeep?
 
Is there an integrated check valve in the regulator? I've been told that's where the factory one lives. Or could one be installed between the regulator and the factory style outlet? I've got that and a fuel rail in my cart already 😊
KennethS said:
That totally makes sense.

I wonder why my ‘98 doesn’t have a similar issue when it’s 115+ degrees here in Phoenix.
Do ‘98s already have a fuel return, or is there something drastically different between years?
What year was your customers Jeep?
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'98s are returnless as well. They all are. The early style intake manifold manifold looks like it blocks the heat from the exhaust manifold a lot better. That's my guess anyways. That and different style injectors.
 
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KennethS said:
That totally makes sense.

I wonder why my ‘98 doesn’t have a similar issue when it’s 115+ degrees here in Phoenix.
Do ‘98s already have a fuel return, or is there something drastically different between years?
What year was your customers Jeep?
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His was a '03. Could be something in the PCM programming. Also the '98 used a different fuel injector than the '00+ if I'm not mistaken.
 
SkylinesSuck said:
Is there an integrated check valve in the regulator? I've been told that's where the factory one lives. Or could one be installed between the regulator and the factory style outlet? I've got that and a fuel rail in my cart already 😊


'98s are returnless as well. They all are. The early style intake manifold manifold looks like it blocks the heat from the exhaust manifold a lot better. That's my guess anyways. That and different style injectors.
Click to expand...

I don't believe there is a separate check valve in the regulator besides the regulator valve itself. I can cut open the one off this pump on Monday and check. I have also read posts before that there is a filter inside the stock regulator before as well. I'm not sure that is true either.
 
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Yeah, the more I thought about it the more I questioned it. If you do cut one open, please share. I did just see the blurb about being able to remove the quick connect outlet fitting and replace it with -6 AN so I guess It would be easy enough to add my own inline as long as there's enough clearance between the tank and the tub.

You mentioned after the mod and last test, the fuel in the rail after heat soak was 300* then dropped by 100* right after you cycled the key. Did it keep falling to ambient? Just curious what the temp of the fuel in the tank gets up to. I had twin Bosch pumps in the Skyline and could actually hear the gas boiling in the tank after sitting in traffic for long periods (on a tropical island) when it was less than half full. I added an inline fuel cooler on the return which solved it for me.
 
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Rickyd said:
You might go one step further and plumb in a fuel cooler like in the return line of my duramax?
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I have seen the aftermatket ones that have the fins on them. I wasn't aware the oems are using them.
 
Jezza said:
I have seen the aftermatket ones that have the fins on them. I wasn't aware the oems are using them.
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I don't know if its warranted in that situation since its a heat soak issue, but they are a nice unit.diesels put a lot of heat back into the fuel
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SkylinesSuck said:
The early style intake manifold manifold looks like it blocks the heat from the exhaust manifold a lot better. That's my guess anyways. That and different style injectors.
Click to expand...

The later models also have two blazing hot catalysts crammed in right under the intake manifold.
 
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SkylinesSuck said:
Yeah, the more I thought about it the more I questioned it. If you do cut one open, please share. I did just see the blurb about being able to remove the quick connect outlet fitting and replace it with -6 AN so I guess It would be easy enough to add my own inline as long as there's enough clearance between the tank and the tub.

You mentioned after the mod and last test, the fuel in the rail after heat soak was 300* then dropped by 100* right after you cycled the key. Did it keep falling to ambient? Just curious what the temp of the fuel in the tank gets up to. I had twin Bosch pumps in the Skyline and could actually hear the gas boiling in the tank after sitting in traffic for long periods (on a tropical island) when it was less than half full. I added an inline fuel cooler on the return which solved it for me.
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I cut it open, and there is no check valve in the regulator. I was surprised to see a built-in paper filter. I was wrong about that part. It has a junky dual spring regulator with a rubber seat. I see why they fail. This one has cracks in the rubber seat that would allow pressure to drop over time.

The longer I ran the engine the closer to ambient temperature the rail would get. It took only a handful of seconds for the rail to drop 100, but then the cooling slowly leveled off. It never got completely to ambient probably due to the feed line being heated and my probe on the back of the rail near cylinder 5. I drove it for 45 minutes or so last week with the return line and the fuel tank was still ambient or just above. I have seen issues with some cars with multiple pumps getting the fuel warm. Mostly on Corvettes where they run 3 pumps with the stock saddle tanks. That's a ton of pump heat in a small area. The fix for that was to stage the pumps in with boost. That also kept the charging system happier as well. I think a small cooler back by the tank would be a good thing to help drop that engine heat off. More volume too.

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Awesome pic! Good to see how it works. And very good to hear the temp kept dropping. Like you said, I think the dual pump setup moving that much fuel is what caused my boiling issues in the Skyline. Sounds like not an issue at all for our TJs. My order was placed over the weekend BTW 😉
 
SkylinesSuck said:
Awesome pic! Good to see how it works. And very good to hear the temp kept dropping. Like you said, I think the dual pump setup moving that much fuel is what caused my boiling issues in the Skyline. Sounds like not an issue at all for our TJs. My order was placed over the weekend BTW 😉
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Multiple pumps create a lot of heat and low fuel levels make it worse. Shouldn't be an issue on the TJ. Some of the older Jeep stuff had return lines and it wasn't until the late 90's they started the return-less garbage. It is cheaper to make.
Thanks for the order. I actually sold out of the return kits this weekend. All of the orders including yours shipped out today.
 
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Hell yeah. I was considering waiting a little to order until I knocked out a few other projects (trying to keep the pending parts pile small). Glad I didn't!! Just curious, are you planning to make more? And feel free to just tag me from now on when you post new products you cook up 😄
 
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