Engine/Transmission (1998.5 - 2002) Autometer Fuel Pressure Guage Acting Weird

[BigMike]

I had a new Autometer electric fuel pressure guage installed in my truck last week. It does not seem to function properly and neither me or the installer can figure out what's going on. When I start the truck cold in the morning, the needle stays on zero. Sometimes after just a couple of minutes it will start bouncing around a bit and then stabalize and give accurate readings. Sometimes it doesn't. It will stay pegged at zero for 10-15 minutes and then suddenly start to work, but not before bouncing up and down between zero and 9 psi. We have checked the power supply. We thought maybe it was air in the system. Now we're at a loss. It only acts this way when I start it cold in the morning. It almost seems like it needs to warm up before it works, which I don't understand. Any ideas we could investigate would be appreciated. By the way, the sender is located on the aft port on the fuel filter housing. When the guage is working properly, it reads 9 psi at idle and 6 psi on the road, with fluctuations down to around 3 when I put a load on it. I'm told those are normal readings. Thanks for your help.



BigMike

 

[Slightly Modified]

Big Mike,

I started to order the Autometer guage like yours since my boost and pyro are Ultralite's, but Geno's Garage said Autometer didn't recommend using that guage on a diesel. Said they wouldn't warranty the sender because they kept crapping out. I bought the westach guage and sender and they are working great. Just put a new lift pump on also and I am getting 15psi at idle, 12 cruising, and 7 with the Comp on 5X5 at WOT.

 

[24V-DSL]

My autometer 0-15 psi electric sender is mounted on the inside fender area just above the fuse box and the line goes to the tapped banjo at the inlet to the VP44. Vibration will kill the senders, so maybe the fuel filter housing generates too much vibration??



Maybe you have a bad sender out of the box.



If you get this resolved and your FP numbers are the same as you state, IMO your numbers are low. I would worry about anything below 6-7 psi no matter what the sample, and be thinking about a new lift pump or worse, VP44 if the numbers stay so low, especially at WOT.

 

[Ray Torresdal]

accuracy?

Have you checked your readings with a mechanical gauge, just for grins??? I just replaced my lift pump, and I'm wondering if my sending unit is not calibrated correctly. I have Westach, and with a new Preporator, am only seeing 10 psi. I'm going to check the readings with a mechanical gauge before I do anything else.



The good news is that I can't pull it under 10 psi, now. Prior, I could bottom it out under heavy throttle.



Ray

 

[BigMike]

We did check it with a mechanical guage. The LP is working fine for now. Some think my pressure readings are low, some think they are ok. Remember, these are pre-filter readings. But my issue still is, "Why doesn't it read consistently and correctly when starting first thing in the morning?" Once it warms up, it works just fine.

 

[CStewart]

I have the Autometer fuel gauge and transducer on my truck and the first transducer I had went bad. I sent an e-mail to customer service and was given a test procedure to verify that the power supply and gauge were working and to test the transducer. I no longer have the procedure but here's a link to the person I talked to. I was also told that the reason that the Autometer transducers are failing with diesel is because of pressure spikes and not vibration. I put a new transducer in with a Chemiquip snubber which dampens out the spikes and have 5000 miles on it with no problems.



Chris



-- email address removed --

 

[BigMike]

I may be wrong, but I don't think I have a transducer problem. Every morning I start my truck, the guage doesn't move. Usually after driving about 3-5 miles, it begins to move and quickly settles into the normal operating range. Very steady and responds to acceleration and deceleration. For the rest of the day, no matter how many times I stop and start my truck, it works perfectly. It seems to me to have something to do with a need to warm-up, but can't explain why. Seems like if it was the transducer, it wouldn't work at all or would be consistently problematic.

 

[BigMike]

Chris, Forgot to say thank you for the email address. I'll send them an email and see what they think.

 

[CStewart]

Hey there Mike,



Cory will give you some test procedures so that you can see if its the power supply the gauge or the transducer. Could be anyone of the three, once you know what voltages to look for where you should know which one is causing the problem. The response on my gauge is within about a second of turning on the key. Hope this helps.



Chris

 

[BigMike]

Appreciate your help Chris. I've already emailed Cory, so hopefully will hear from him tomorrow. Sure like to solve this problem.

 

[Warpig]

Originally posted by CStewart

I have the Autometer fuel gauge and transducer on my truck and the first transducer I had went bad. I sent an e-mail to customer service and was given a test procedure to verify that the power supply and gauge were working and to test the transducer. I no longer have the procedure but here's a link to the person I talked to. I was also told that the reason that the Autometer transducers are failing with diesel is because of pressure spikes and not vibration. I put a new transducer in with a Chemiquip snubber which dampens out the spikes and have 5000 miles on it with no problems.



Chris



-- email address removed --

CStewart, Could you explain your fix in detail for me. I have new Autometer guages, and the fp guage is acting erratic. I have the F. A. S. S. fuel system and my transducer is plugged in to the vp44. What is a chemiquip snubber and where can I get one.

Thanx,

Tim W.

 

[CStewart]

Sorry War but I don't remember the exact specs. and I wouldn't want to give anyone the wrong values. I have my transducer hooked into the factory filter housing on my truck and I do notice that the fuel pressure moves up and down about 3 psi until the truck or maybe the FASS has a chance to warm up. It is nice and steady at idle and only moves about 1 psi when I put my foot in it. A chemiquip snubber is used in industrial instrumentation do dampen out pulsation and give a steady reading and prevent damage to a transducer which is somewhat sensitive. It looks like a small brass fitting that is 1/8 male on one end and 1/8 female on the other with a sintered metal disc in between. How fine the porosity of the disc is determines how restrictive the snubber is, I'm using a PN# 12BE which stands for 1/8 NPT brass porosity E. It is also available in SS if you want something a little stronger in case you are subjecting the snubber itself to a lot of vibration. I have 5000 miles on a brass one with no problems. Its a common hydraulic/ instrumentation part that you should be able to locate a source for through the Internet. I got mine locally from a former employer here in the chicago area. Hope this helps!



Chris

 

[CStewart]

Did some digging and found that I had saved that E-mail after all:



Red is a 5volt supply to the sender from the gauge. Black is ground.

White is the signal return. With the power on and no fuel pressure

present, you should see 5 volts at the red wire and 0. 5volts on the

white wire. If you see this, then the sender is ok, and the gauge or the

control box is malfunctions and in need of being sent in for service.

15psi, you should see 4. 5 volts on the white wire. If you see this (when

there is no pressure), then the sender is at fault for giving the gauge

the wrong information.



The reason we do not recommend that gauge with the diesels is due

> to the pressure spikes in the fuel system.

> Tell me what color wires are at the sending unit ( we have revised

> them, so colors may vary) and I will tell you how to test it. Also, do

> you still have a photo copy of your original receipt? If so, I still

> may be able to help you with this.

> We have not yet revised them to be compatible with the diesels

> yet, but we are working on that as well.

> I will wait to here from you.

> Thank you

> Cory

> Tech/Service



Found the original message too

 

[Warpig]

Snubber

Thanx for the info CStewart. I will try a snubber.



Tim W.

 

[BigMike]

Chris, Got a response from Cory this morning. Here's what he said:



"I recommend at this point that you send the gauge in to us to test. We can

chill the gauge and test it to see if the gauge is indeed failing cold. You are

welcome to send it in to us at:

Auto Meter Products

Attention Service

413 W Elm St.

Sycamore IL 60178



Please include your name address and phone number as well as a description

of the problem. You may also ask that we freeze the gauge prior to testing or

just include a copy of this e mail when you send it in.

Thank you.

Cory

Tech/Service"



I think I might take it back to the folks I bought it from and who installed it and have them take care of it.

 

[Chipstien]

Good luck. I went through 4 senders in 6 months before I ditched the Autometer electric FP guage and went to the mechanical guage. And I was running a snubber too. As been said, AM senders will not hold up under Diesel. I am surprised that they have not updated the senders to work with diesel yet.

 

[BigMike]

Chipstien, According to the guy that installed mine, the literature with the gauge listed just about every kind of fuel, including diesel, as being compatible with the gauge. Maybe they've updated them.

 

[Bobalos]

I sure hope

that AutoMeter has thier stuff together, because I just got done spending 6 Bills on gauges on my truck & would be VERY ticked off if the FP gauge dies in a few months. I have Used Auto Meter on all my Hot Rods for years & would be pretty bummed if this does not work.



I do have the sending unit isolated over by the fender so vibration should not be an issue.



bob

 

[Warpig]

Snubber

CStewart,



I found a chemiquip snubber thanx to you. I installed it tonight, and after a test run, and 30 miles everything works great. 20 psi at idle and under wot with no erratic movement. You were right on the money. Ya gotta love the TDR and great people like you!



Thank you,



Tim W.

 

[24V-DSL]

Thanks to both Cory at Autometer, and CStewart I contacted Chemiquip Products in New Jersey 201. 868. 4445. They will provide a local source for the snubbers by giving them your area code. Ordered mine from Branon Instruments in Ptld. Or. 503. 283. 2555.



I've had my Autometer electric guage for over three years with no problems, but figure the snubber is good insurance.