Fuel Pressure Switch and Hard Starting CUCV

[stuinnh]

If your CUCV is hard starting in 60+ degree weather (and lower) you need to replace the fuel sensor switch located in the Stanadyne 80 fuel filter base. It is round with two wires and held in place with a round spring clipunder the filter. They crack with age and you may or may not see it leaking. Replace it! $10 item. At first I replaced glow plugs, put check valve in fuel line, and finally put electric fuel pump in fuel line. Nothing worked. I then found out the military was aware of this and was replacing them. They are not in civy models, only in military trucks, part of the ice testing system. I spent a lot of money finding this out. When they are bad, it will seem there is a drain back problem and a problem getting fuel through the system and it is very hard to start in all temp weather. All CUCV owners, change the fuel sensor switch!
Expensive lesson for me.....when I replaced the glow plugs and tightened them down using new Sears torque wrench, I snapped all eight plugs, had to be towed to shop and $1100 later I returned the wrench. When I arrived home from the shop 2 days later, I noticed oil puddle under truck when I parked it and another $200 later I had new high pressure oil lines. They blew on the ride home. Owen's Export had the fuel pressure switches for $10. Oh, I also replaced the fuel heater (on top of the fuel filter base) too before figuring it out. Oh, I also replaced glow plug temp sensor.

 

[Recovry4x4]

This is good info. All CUCV owners should be aware of it. BTW, how did you find Owens Ex to have them? They used to have a pretty detailed website but lately its a dud!

 

[kipman]

Replace the stock filter set up with a up grade spin on, do a search here, I thinks some of the cucv owners got the set up at wally world.

 

[kapnklug]

If the fuel pressure switch isnt found in the civvy trucks at all, why not just bypass it and save the $10? Which is what you'd have to do when upgrading to a spin-on anyway. Would you connect the two wires to bypass it, or separate them?

 

[YellowHammer]

Part #???

 

[stuinnh]

Hard starting COCV's

No #. Only military used it. Not available from GM.

Sometimes you can see them leaking, or not. If CUCV is hard starting in warm weather, and/or you need the block heater in winter, change fuel pressure switch first (cheaper than replacing glow plugs).

 

[123mack]

I looked at the spin on thread and didn't see anything about the fuel pressure switch. So, how do you bypass it?

 

[doghead]

I looked at the spin on thread and didn't see anything about the fuel pressure switch. So, how do you bypass it?

The fuel pressure sensor is used for data collected by the Ste/Ice test equipment. It is not needed, just leave it disconnected if you convert the fuel filter to something else.

 

[wildcat]

Fuel pressure sensor switch

My truck exhibits similar characteristics. Where can I get the "fuel sensor switch"? Local auto parts store or military supplier? Also I have a reoccuring water in my fuel tank problem. I have drained gallons out of the filter assembly over the last year. Is it condensation? Is the tank not breathing correctly or is it from rain? Any thoughts? The 3 lines coming from the tank are supply, return and "drain"? Should the "drain" be plugged off? Thanks.

 

[stuinnh]

My truck exhibits similar characteristics. Where can I get the "fuel sensor switch"? Local auto parts store or military supplier? Also I have a reoccuring water in my fuel tank problem. I have drained gallons out of the filter assembly over the last year. Is it condensation? Is the tank not breathing correctly or is it from rain? Any thoughts? The 3 lines coming from the tank are supply, return and "drain"? Should the "drain" be plugged off? Thanks.

Got my fuel sensor switch from Owens Export Service -818-772-0806

www.owens-export.com

 

[stampy]

Bypassing made sense for me running bio, but thanks for the info! Spin on filters are easy to change, and cheaper too.

 

[kentuckycucv]

Dog head said it stuinnh... I have to agree that the "fuel pressure" has nothing to do with your truck not starting due to "fuel pressure" .... It only collects data for a plug in STE-ICE computer. BUUUUT when it goes bad like mine did it lets AIR get into the fuel system. Its not lack of heat, pressure or anything else. It wont start because of air in your inector, and IP. My fix was after trying new O rings for it....I disconected my fuel pressure switch, bought a 1/4 tap and stuck a 1/4 screw in the hole behind the pressure switch, and blocked it off. The pressure switch is just hanging there now.

Another thing I learned is that the switch lets air into the filter. To bleed the air out you open the valve on top of the filter. You disconect the pink wire on the injection pump. you crank until fuel comes out of that top screw port you just openened on your fuel filter. then close that valve hook up the pink wire on the IP then your truck will fire up with a turn of the key.

I learned all that on here.... this site kicks ass! Lots and lots of talk about that pressure switch on here.

 

[customfitch]

This seems to be the symptoms I am experiencing with my M1108 now. The problem is intermittent; sometimes the symptoms disappear, then return suddenly. Def. seems to be getting air into the system somewhere. I will start with bypassing this switch and see what happens.

 

[CUCV85]

progress report requested

This seems to be the symptoms I am experiencing with my M1108 now. The problem is intermittent; sometimes the symptoms disappear, then return suddenly. Def. seems to be getting air into the system somewhere. I will start with bypassing this switch and see what happens.

Let us know how that works out, pluging that off with a screw. I think I may have to do this with 2 that my family owns. Crank crank crank like 5 to 8 seconds. They must be getting air into the system.

 

[SmokeyDod]

Stu, Just for you or others to consider,-- I just ran into similar problem of not starting with M1028 I just sold yesterday. Truck would turn over w/o any problem but was hard to get running. Then it might run 3-5 min or in some cases 15 min. any then cut off. I installed brand new OEM stanadyne unit w/filter. Same senerio. It wasn't getting fuel to the filter unit so I put on another fuel pump (not IP). Same problem. Tried blowing air into the fuel tank and it seemed to work for short time (30-45 min). After all lines checked with out finding any leaks. I took off fuel tank and removed the fuel sender unit. It was AMAZING how clogged up the unit's sock was. There was also lots off "crud" in bottom of tank.

We drained all but a couple of gallons of fuel and then added about a quart of rocks from my driveway and shook it out & back for 15 min or so, then removed rocks and fuel. Then we rinsed it out with water & hose pipe thourghly and then re-rinsed out a couple of times with diesel. Installed the tank on trunk, added fuel. It finally works perfectly now.

 

[SmokeyDod]

I also mean't to say to "Wilcat" that the 3 lines coming off top of tank are as you said one is fuel line, one is "return" line but the little short one with the rubber cap is not a drain. Its for use with trucks that have duel tanks and this is connection for that.

 

[pappydodd]

FYI, I just ordered the fuel sensor switch from Owens Export. The price has gone up to $20 plus $6 for shipping, but they do have them in stock. If it fixes the problem, it will be worth it. Also, when I first got the truck, if I let the fuel get below half a tank it would stall on the highway. Culprit was a hard fuel line that had rubbed against the frame. The pressure of a full tank prevented it from sucking air; low fuel/less weight. I cut a section of the line out, flared the ends and used a piece of flexible hose.

 

[stuinnh]

FYI, I just ordered the fuel sensor switch from Owens Export. The price has gone up to $20 plus $6 for shipping, but they do have them in stock. If it fixes the problem, it will be worth it. Also, when I first got the truck, if I let the fuel get below half a tank it would stall on the highway. Culprit was a hard fuel line that had rubbed against the frame. The pressure of a full tank prevented it from sucking air; low fuel/less weight. I cut a section of the line out, flared the ends and used a piece of flexible hose.

Let me know how it works out.
Stu

 

[stuinnh]

FYI, I just ordered the fuel sensor switch from Owens Export. The price has gone up to $20 plus $6 for shipping, but they do have them in stock. If it fixes the problem, it will be worth it. Also, when I first got the truck, if I let the fuel get below half a tank it would stall on the highway. Culprit was a hard fuel line that had rubbed against the frame. The pressure of a full tank prevented it from sucking air; low fuel/less weight. I cut a section of the line out, flared the ends and used a piece of flexible hose.

In my M1008, the fire dept. put new filter system in. Sold it off because they couldn't start it most of the time. When I received it, it was converted to 12v. But, it was still wired to resister before going to glow plugs. Easy fix, runs great for 8 years now.

 

[pappydodd]

Thank you for the excellent advise. THis is the best $26 I have ever spent. For the first time in three years the truck started this morning and kept running--just tapped the fuel, waited for the glow plugs to cycle, cranked and it started and ran. Temperature was about 25 degrees. This is a first for me and this truck. Also, the part I got from Owen's (a great place for parts and an interesting guy to talk to) was a type 3. The instructions say you need a special tool available from the manufacturer. I believe the tool is to help prevent damage to the part, but I used my thumbs after lubricating the O-ring, and it seemed to work fine, and the new-style retaining clip that is attched to the part was easy to get in place with a screw driver. Thanks again--this is a great place to start for anyone who is having problems with air getting into the fuel system on a 1008.