BTW....
How does a "cold" humming noise differ from a "warm" humming noise?
BTW....
How does a "cold" humming noise differ from a "warm" humming noise?
Well, what I was suggesting - in my experience - good fuel pumps may make noise when Hot - a lot of noise. A loud hum like a deep siren noise of sorts. No noise when cold except for the regular low hum of the motor.Quote:
Originally Posted by cpistocco
Over the years I have experienced the noise in three different DeLoreans. Changing fuel pumps never helped. It seemed to be made because of "over heating" fuel (hot enough to cause the fuel pump to make the awful noise). I addressed that as the issue because, when the noise occurred, if I put in cold fuel at a gas stop, the noise was gone when I started up to leave and did not return for quite some time, if I kept driving. The Hot fuel appeared to be caused by the coolant lines laying against the fuel tank where the coolant lines pass through the frame at the tank. I put an insulating hose around the coolant pipes from behind without dropping the tank - just dropping the back of the cover some. The noise was gone for several years until this spring.
I found the Loud noise occurred again this spring when the fuel tank pressurized - a lot -because the fuel "rollover valve" was stuck closed. I think there was a heat built up in the fuel because the tank expanded and pushed against the coolant lines as the pressure rose. The noise hasn't returned since I fixed that. I am concerned that my homemade heat shield may have been damaged because of the pressure and I may experience some heat issues again when I drive this summer.
I believe the hot fuel pump noise can also be caused by the usual bad electrical connections causing the pump to get hot. Those should be checked regularly. The connections at the pump, at the gang plug in the window washer bottle compartment, the ground through the rollover switch, the RPM relay connections and fuses, etc.
I instrumented my gas tank and fuel return line and found the return line temp was always a few degrees warmer than the gas in the tank. So the gas in the tank would continue to increase in temperature the longer the engine was running. My fuel pump would buzz when the gas went above 120 deg. F in the tank. Now the coolant lines running beside the tank may add to the problem but I think most of the heat comes from the engine heated fuel returned to the tank.
I have not had any pump buzz since installing my return line cooler I installed years back.
Thank You both for the info..... I cant believe that there are so many quirks to this car......were any real engineers involved in its development? :) But we still haven't figured out what the accumulator replacement has to do with the noise.
My guess is - the leaking accumulator allowed cooler fuel to by-pass a trip through the hot engine compartment. Now all excess fuel passes through the engine compartment and heats up on it's return to the fuel tank. The hot fuel issue is just another product of the short life of the original DMC. There are so many CIS systems out there but, from my observation, the DeLorean is the only car that has the fuel tank in an area that gets exposed to consistent heat from the engine by fuel passing through engine compartment and back to a fuel tank exposed to heat from the radiator. I also suspect that not all fuel pumps react to the heat the same way. The fuel pump on my current DeLorean has been in at least 20 years and it gets the hum, or roar, when it gets overly hot. Maybe a new (I mean newly manufactured, not NOS) would tolerate the heat much better. I believe also that electrical issues contribute to the DeLorean problems of the fuel pump - poor connections and grounds.Quote:
Originally Posted by cpistocco
That's very clever Dave but besides possibly affecting A/C temps aren't you worried about the chance of fire? Though it may seem remote the A/C accumulator is essentially behind (agreed it's to the inboard side) the R/F tire and the copper tubing could be easily pierced by road debris resulting in a massive fuel leak over the entire R/H flank of the car. Just wondering if you considered that? We'd hate to lose you in a giant fireball as it would be a modern day premature Viking funeral! Perhaps at least put shielding of some sort over it?Quote:
Originally Posted by Bitsyncmaster
Rob
Delorean employed many engineers both directly and indirectly not to mention the Bosch engineers that originally designed CIS. As they say the devil is in the details and the details were the devil in the breakneck pace to both design a car and build a factory to assemble it in a few years time. It had never been done that quickly before as Barrie Wills book will attest to.Quote:
Originally Posted by cpistocco
Rob
Is there such a thing as a fuel rad? Something similar to a transmission cooler? A small motorcycle rad would work too, but are they not used simply because of the fire concerns? Do they really add that much risk?Quote:
Originally Posted by PJ Grady Inc.
Something like this
http://uploads.tapatalk-cdn.com/2016...5f69181fc9.jpg
Yes I considered the AC might not work as good but it does not seem to have effected the AC performance.Quote:
Originally Posted by PJ Grady Inc.
That copper tube is pretty heavy soft copper. I guess the chance of road debris hitting it is very remote and since is soft copper it probably would just dent it. There is some epoxy covering the ends to hold it tight onto the accumulator. There is no pressure in the return line so I feel it's pretty safe.
There are fuel coolers that racers use to chill the fuel to make it denser but they are basically a big bottle filled with ice chips that has a small coil that the fuel runs through. Using the A/C to cool the fuel is not unusual. If you are worried about the copper getting damaged, just wrap a piece of sheet metal or plastic (probably a better choice) over it. Another source of heat is the coolant lines running alongside the bottom of the tank. The other thing that has been done is to hang a piece of rubber over the front of the fuel tank to keep the hot air from the radiator fans off of the tank and it deflects the air under the car. Once the pick-up hose gets hot it softens up and kinks or collapses under the vacuum from the fuel pump. When that happens the fuel pump starts "singing". It needs all of that fuel flow to lubricate and cool it. Without full flow it makes a lot of noise till it dies. Another "tip" is to put a spring inside the hose so it won't collapse. Once the pump starts getting loud it is damaged and will just get louder.