OEM Fuel Cooler Replacement

Topic: OEM Fuel Cooler Replacement (Read 2220 times) previous topic - next topic

OEM Fuel Cooler Replacement

September 13, 2019, 12:09:07 pm

Looking for some wisdom from the forum. I am going to replace the OEM Fuel cooler which appears to be a tube and fin cooler with one tube that makes three passes through the fins. I have no idea whether or not there are internal turbulence generators inside the tubing, but it didn't seem to flow air as freely as I was expecting it to. Anyway, since I have been having an intermittent stop engine light which has proved intractable to lower level cheap fixes. I am working my way up to a CAPS replacement pump through all the cheaper options. I figure that way, I will fix the questionable (in my mind) support infra structure that feeds the CAPS injection pump assembly fuel. That has included new fuel lines (done at FOT prior to the stop engine light issues), removing 90º elbows (a total of about 9) and replacing them with long radius sweeps. Upgrading from the Racor R90P to DAVCO 382 primary fuel filter/water separator, replaced several sensors.

I added A fuel temperature gauge to my VMSpc (PID174) and the temperature runs consistently higher than the 140º that Cummins says should be the max fuel inlet temperature. It has run as high as 162º. The only fuel temperature sensor that I am aware of is right on the CAPS pump assembly, and that sensor is new. The temperatures shown on the new sensor are about the same as the one it replaced. Unfortunately, I never had a gage set up to monitor fuel temperature prior to the intermittent stop engine light issues, so I am not sure how much high fuel temperature might be affecting the situation, but cooler fuel couldn't hurt so I am going to address the issue.

When discussions about fuel coolers occur on the forum, transmission coolers are commonly mentioned as possible choices. There doesn't seem to be a product category specifically for diesel fuel coolers. Hayden has a whole line of coolers of different sizes and form factors, as well as different types of coolers. Tube and fin is the most common one and these consist of one or more lengths of tubing which are in rows. Bar and plate is another type and is more space efficient for the amount of cooling. Hayden makes both types, but has many more size and form factor options for the tube and fin type. At the moment, I am considering two different options: Hayden 1260 HD tube and fin and a Hayden 801 HD Commercial. Attached are a couple of screen captures from the Hayden Catalog. I am leaning toward the 801 bar and plated model for the smaller form factor, but the 1260 would be an easier installation because of the current fuel cooler mounting and compatibility of the fittings. However, the 1260 at 12" high is about twice the height of the OEM. Our coolant temperatures are not a problem and never have been, but I am reluctant to decrease the airflow through the radiator. Thoughts, questions?

Re: OEM Fuel Cooler Replacement

Reply #1 – September 13, 2019, 01:11:26 pm

Several trans coolers have their own fan so you don't have to worry where you mount them. For newbies, RVs have fuel tanks that don't get the cooling that big rigs do with their tanks out in the airstream. Each engine will have the recommended max fuel temperature.

Cummins lift pumps are poor quality and can cause main injection pump failures. Also cause the light to come on. Are you sure this is not your problem? Possible replacement with electric pump?

Quite a few Cummins owners have dumped the CAPS pump and replaced it with a Bosch P pump. While the CAPS pumps have improved a lot, they still fail and each failure costs a lot of $$$. Over the the counter conversion kits are about $8K but pumps, lines, etc can be found for much less. The P pumps will outlast several engines. I have a bunch of used ones in a box but for 4 cylinder Mercedes so won't do you a lot of good. I got them for $25/each so the deals are out there for any Bosch P pump. I would think a good used P pump would be about $500 for an 8.3 but check the images and the links for new prices. Even at $2K, the rest of the parts are not that expensive. replacing 8.3 CAPS pump with a Bosch P pump - Google Search

Pierce

Re: OEM Fuel Cooler Replacement

Reply #2 – September 13, 2019, 03:30:01 pm

Hi Don,

I am sorry but I do not have any thoughts or insights into your stop engine problem. However, thank you for mentioning the VMSpc fuel temperature gauge. I had never noticed before but just added it to my display. It will be another interesting bit of information to have.

Richard

Re: OEM Fuel Cooler Replacement

Reply #3 – September 13, 2019, 04:48:11 pm

Thanks for trying that Richard. Have you tried that gauge with the key on to see if you get a reading? It would be a good data point to see where the ISM fuel temperature sensor is in relationship to ISC. George Hatfield and John Haygarth both tried PID174 and it didn't do anything. They both have ISC's a year or so later than ours, but certainly the Cummins ECM uses the information for its own uses, it should be available. I would be great if someone else with a 99' ISC would try making a new gage with that PID so we can compare results. Or if someone who has a 200 ISC or later can get a fuel temperature gauge working...
Don

Quote from: Jan & Richard – September 13, 2019, 03:30:01 pm

Hi Don,

I am sorry but I do not have any thoughts or insights into your stop engine problem. However, thank you for mentioning the VMSpc fuel temperature gauge. I had never noticed before but just added it to my display. It will be another interesting bit of information to have.

Richard

Re: OEM Fuel Cooler Replacement

Reply #4 – September 13, 2019, 05:00:06 pm

Pierce, thanks for the info...
Starting with the 1999 model year, Cummins went to the electronic engine and the CAPS fuel injection pump. They went to common rail around 2005. Anyway, the electronic lift pump only runs for 30~45 seconds with a key on event to prime the gear pump part of the CAPS pump assembly. After that the entire fuel supply line is under suction from the CAPS gear pump. Probably a 22' long straw to suck the fuel through. I believe that fact is the Achilles heel of the 98.5' though 2005 ISC or ISL. That is if they didn't make changes in the lift pump functionality. The fuel cooler is a part of a more involved project to add an adjustable HD FASS full time lift pump to feed the CAPS gear pump a low positive pressure, between 5~15psi at whatever volume is required. The excess fuel returns through the fuel cooler loop which I am talking about in the thread starter.
Don

Quote from: Pierce & Gaylie Stewart – September 13, 2019, 01:11:26 pm

Cummins lift pumps are poor quality and can cause main injection pump failures. Also cause the light to come on. Are you sure this is not your problem? Possible replacement with electric pump?

Pierce

Re: OEM Fuel Cooler Replacement

Reply #5 – September 13, 2019, 05:54:51 pm

Don when did you see the temperature at 140° running down the road or idling ?

Re: OEM Fuel Cooler Replacement

Reply #6 – September 13, 2019, 05:56:13 pm

Have you disconnected the outlet of the fuel cooler to see what kind of flow was going through the cooler ?

Re: OEM Fuel Cooler Replacement

Reply #7 – September 13, 2019, 07:05:13 pm

Quote from: Don & Tys – September 13, 2019, 05:00:06 pm

Pierce, thanks for the info...
Starting with the 1999 model year, Cummins went to the electronic engine and the CAPS fuel injection pump. They went to common rail around 2005.

I was thinking to make the engine mechanical for models up to the common rail models. That is what the kits are for. Don't know if the kits would fit the head from 2005 on but would violate EPA rules. Some people were getting burned with the CAPS pumps two or three times.

Any kind of trans cooler will flow plenty of fuel and a lot more than the hose can flow.

P

Re: OEM Fuel Cooler Replacement

Reply #8 – September 13, 2019, 07:50:21 pm

Good thought! I meant to do that when replacing all of the 90's in the cooler loop but tan short of time.
"Have you disconnected the outlet of the fuel cooler to see what kind of flow was going through the cooler ?"

Re: OEM Fuel Cooler Replacement

Reply #9 – September 13, 2019, 09:02:35 pm

Seems unlikely the fuel temp being slightly over preferred is triggering a failure mode. Have you logged fuel tank temps when error occurs?

Re: OEM Fuel Cooler Replacement

Reply #10 – September 13, 2019, 09:19:07 pm

Cooler efficiency is primarily a function of wetted surface area.
The greater the wetted surface of the fluid:
1) to be cooled (fuel)
2) of the cooling fluid (air)
The more efficient the cooler is...

I vote for the Hayden Plate & Fin Trans coolers

Re: OEM Fuel Cooler Replacement

Reply #11 – September 14, 2019, 12:16:29 am

Don : Just ordered will keep you posted of my findings and results . FASS Fuel System RPDRP DRP Replacement Pump 1998-2002 Fits Dodge Cummins Diesel

Re: OEM Fuel Cooler Replacement

Reply #12 – September 14, 2019, 02:07:36 am

I am buying the FASS UP95 unit from UltraRV products. It costs more than Summit Racing, but the guy who packages the FASS pump modifies the harness that comes with it so that the Cummins ECM doesn't know the Electronic lift pump isn't connected anymore. He claims he has done this for many Cummins CAPS equipped RV's with good results. This method bypasses and plugs the fuel inlet and outlet on the supply side of the OEM lift pump. The OEM electronic lift pump has an integral manifold that takes the unburned return fuel after it cools the CAPS Assy., the engine's ECM, and feeds the injectors. The OEM pump stay's mounted in place on the side of block and the return lines stay as before. He also told me that a not uncommon problem with the CAPS equipped coaches is tha the lift pump seals can develop an internal leak that lets air into the system. The Cummins price on the OEM Electronic lift pumps are more than half the cost of the heavy duty FASS pump and are a royal PITA to install. I regret that I misplaced the one I took out that failed when it started leaking diesel, because I would like to dissect it. I may yet find it in storage somewhere, but not in time to do me any good now... Anyway, I am going to order my pump on Monday, and probably have it by Wednesday. Perhaps between us we can add to the knowledge base on the forum. I intend to document the project as well as I can. I look forward to hearing about your results.
Don

Quote from: opelgt327 – September 14, 2019, 12:16:29 am

Don : Just ordered will keep you posted of my findings and results . FASS Fuel System RPDRP DRP Replacement Pump 1998-2002 Fits Dodge Cummins Diesel

Re: OEM Fuel Cooler Replacement

Reply #13 – September 14, 2019, 02:09:38 am

Sadly, no. But I do notice that it occurs more frequently as the indicated temperature on my VMSpc gage rises.
Don

Quote from: Chuck Pearson – September 13, 2019, 09:02:35 pm

Seems unlikely the fuel temp being slightly over preferred is triggering a failure mode. Have you logged fuel tank temps when error occurs?

Re: OEM Fuel Cooler Replacement

Reply #14 – September 14, 2019, 02:15:52 am

Always while running. It starts off at ambient air temperature and by the time the coach is warmed up the fuel temperature is somewhere around 125º. The temperature gradually rises to between 145º and 160º. This range doesn't seem to change much when the tank is fuller rather than emptier, but is higher on hotter days.
Don

Quote from: opelgt327 – September 13, 2019, 05:54:51 pm

Don when did you see the temperature at 140° running down the road or idling ?

Re: OEM Fuel Cooler Replacement

Reply #15 – September 14, 2019, 03:21:21 am

Don,

I fit one of the Hayden transmission coolers on our U240 in the fuel return line to the tank. Size for your larger engine would be larger, so no specific PN recommendation.

I placed it in the air flow in front of the CAC. Dianne made a cover for it from canvas with velcro fitting so it could be covered in winter. Yes, the fuel can get too cold if driving in below freezing temperatures with a fuel cooler exposed.

Re: OEM Fuel Cooler Replacement

Reply #16 – September 14, 2019, 10:31:16 am

Quote from: Don & Tys – September 14, 2019, 02:15:52 am

Always while running. It starts off at ambient air temperature and by the time the coach is warmed up the fuel temperature is somewhere around 125º. The temperature gradually rises to between 145º and 160º. This range doesn't seem to change much when the tank is fuller rather than emptier, but is higher on hotter days.
Don

Don, one thought is that fuel is cool coming from tank initially, so it's being warmed by engine heat. Are you able to position the cooler where it can shed the added heat immediately before injection pump? Or is injection pump what's warming the fuel? The heater is not energized on the Davco by any chance?

Re: OEM Fuel Cooler Replacement

Reply #17 – September 14, 2019, 11:31:52 am

Quote from: wolfe10 – September 14, 2019, 03:21:21 am

Don,

I fit one of the Hayden transmission coolers on our U240 in the fuel return line to the tank. Size for your larger engine would be larger, so no specific PN recommendation.

I placed it in the air flow in front of the CAC. Dianne made a cover for it from canvas with velcro fitting so it could be covered in winter. Yes, the fuel can get too cold if driving in below freezing temperatures with a fuel cooler exposed.

Brett,
How does the fuel get too cold in such a short distance after leaving the fuel rail as hot as it is?

Re: OEM Fuel Cooler Replacement

Reply #18 – September 14, 2019, 12:20:52 pm

Since the fuel cooler is in the return line, it doesn't seem like it the fuel coming out of the tank could all be heated anything close to 140º let alone 160º+, so much of the heating read by the pump mounted sensor must be engine heat. The supply fuel comes into the lift pump after the Davco primary (btw, I haven't hooked up the heating element on that yet so not a factor) where it is in close proximity to the unburned fuel coming out of the head. From there through a steel tube into the block mounted secondary filter. There is a short braided flexible hose with a couple of JIC swivels on to an elbow at the bottom of the gear pump. I don't know if the sensor reads the temperature before the gear pump or after. Still, since I don't know yet what is normal for that sensor reading, it may the same as other 99' ISC's. Since I will remote mount the FASS lift pump and bypass the OEM lift pump on the supply side of it (still using the return portion of the manifold part of the OEM lift pump assembly), the fuel coming from the tank won't see any engine heat to speak of until it enters the secondary filter. That should help lower the incoming fuel some.
Don

Quote from: Chuck Pearson – September 14, 2019, 10:31:16 am

Don, one thought is that fuel is cool coming from tank initially, so it's being warmed by engine heat. Are you able to position the cooler where it can shed the added heat immediately before injection pump? Or is injection pump what's warming the fuel? The heater is not energized on the Davco by any chance?

Re: OEM Fuel Cooler Replacement

Reply #19 – September 14, 2019, 08:00:42 pm

Quote from: craneman – September 14, 2019, 11:31:52 am

Brett,
How does the fuel get too cold in such a short distance after leaving the fuel rail as hot as it is?

Not a matter of "too cold in the short distance between engine and fuel cooler. But the fuel cooler is very efficient at reducing fuel temperature very close to ambient before its return to the tank. No desire for under 30 degree fuel temperature.

Re: OEM Fuel Cooler Replacement

Reply #20 – September 17, 2019, 01:21:07 am

I did an abbreviated test to see how much fuel came out of the return line of the OEM fuel cooler. Just dribbled out with the OEM electronic lift pump and a steady but minuscule flow with the engine idling. I have decided to order a new one from Amazon to be delivered to the campground. Not the cheapest option, but it should be superior to the stock unit. I might go another way if I was home, but I am bypassing the OEM electronic lift pump as described earlier. Ordering a gauge will be next...
Amazon.com: Mishimoto MMOC-DP-LSL Silver Bar and Plate Oil Cooler (Universal...

More on this part of the project later.
Don

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.

Re: OEM Fuel Cooler Replacement

Reply #21 – September 17, 2019, 10:58:04 am

Our fuel tank gets too hot to touch if the level is more than half way down. On the way to the unit injectors, it passes through the DDEC ECU and is supposed to cool it just before the fuel goes into the cylinder heads (yes, cylinder heads, no injector pipes). A cooler on the return line to the tank would be an excellent idea. It could be plumbed to be bypassed in winter.

Pierce

Re: OEM Fuel Cooler Replacement

Reply #22 – September 18, 2019, 09:54:54 am

I have enjoyed reading about all the stuff you folks do with your coaches but have to say that Don's vast quantity and quality of work as well as his knowledgeable write-ups is by far the leader. I have often thought that Don does things to be "doing things". Like maybe changing one of the 90's today then another tomorrow and so-forth until they have all been addresses. Don seems to be driven and I have really appreciated him and his reports. I'm a good "front porch" mechanic enjoying sitting and watching others do the work. All you guys keep going. Thanks for the entertainment!

Re: OEM Fuel Cooler Replacement

Reply #23 – September 18, 2019, 08:53:43 pm

Yes Don is a perfectionist as I have seen him Work a few times
The fuel line issues, or should I say redu of 90s with copper tube was done while they visited us a month or so ago and much care was given to doing them.
Tys has resolved to accept whatever time line is needed to get the jobs done.
Nice work to say the least
JohnH

Re: OEM Fuel Cooler Replacement

Reply #24 – September 18, 2019, 10:58:46 pm

Thanks for the kind words. The fuel cooler is supposed to arrive here at the RV park tomorrow. I am hoping to install it and the new fuel pump in one day... we'll see about that. I have already bought the necessary fittings to mate up with the rest of the fuel plumbing at a local full service hydraulic shop. I am sure I will be going back there tomorrow once I figure out which fittings I need to plug the OEM fuel pump inlet and outlets. I have yet to identify the threads on the secondary filter's I/O port, but I think id may be an AN10 or AN12 or the JIC equivalent. Tomorrow will tell. That is the subject of an up and coming thread or resurrection of an earlier one.
Don

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