Replacing the fuel filter

[Bitsyncmaster]

I'm sure many of you have tried to replace your fuel filter and found that pipe feed line frozen in the compression elbow. Well mine is the same and first time I replaced the filter I left the pipe in the elbow and just unscrewed the filter from the NPT threaded end. This is a pain to do since you need to get that top hose connected and torqued with the copper crush washers. I guess many owners have damaged that feed line pipe trying to get it removed.

I could do the same and just twist the new filter back onto the NPT thread. But I was thinking maybe just install the 1/4" NPT to hose nipple on the filter and use 5/16" high pressure fuel hose. It looks like the pipe is 5/16" OD but if I cut off that frozen elbow then there will be no "barb" for the hose to hold onto. I would think two good hose clamps would work. Or I may be able to use a new compression fitting going to a 5/16" hose barb on the cut pipe.

Have any owners done this?

Also, why do they use foam between the filter and the mounting clamp?

[Helirich]

Sounds like good ideas. Please take pics.

[David T]

The fuel system in a Delorean is high pressure, higher than typical fuel injection systems. I would not recommend just slipping a hose onto a pipe without have a bead on the end. The reason those fittings are so tight is that they are steel, not copper and to deform it enough so it doesn't leak requires a LOT of force to tighten or loosen it. If you are going to use hose clamps and no bead at least put two clamps on each end of the hose and make sure the hose you use is rated for Ethanol and the pressure. Whatever you do DO NOT TWIST THE FUEL LINE! If you kink or twist the fuel line the only way to replace it is to remove the body. What some have done in the past if they wrecked the line is to abandon it and run another line. Not the best or cleanest solution but it does work.

[DMCMW Dave]

Have any owners done this?

Also, why do they use foam between the filter and the mounting clamp?

I have not seen it done exactly as you describe. I wouldn't be comfortable with the rubber hose on a non-barbed fitting. If you can find a compression fitting that is barbed on the other end that would be more acceptable. This is essentially what is done at the accumulator. Use the same hose and the same fuel-injection type clamps. Keep in mind that a fuel leak at the accumulator just falls out of the hole in the frame, where a fuel leak at the filter would spray all over the exhaust system. BE sure that there isn't excessive play in your setup, i.e. might need a bracket to support the fuel line a bit more since it would now be supported only by the rubber hose at that end.

The foam gasket is probably to keep the aluminum filter from touching the steel bracket (encourages corrosion due to dissimilar metals). Although the steel hose connection is not really different.

[Bitsyncmaster]

Well I decided to do it the old way and leave the supply pipe as is. Just have to guess when torquing the top banjo bolt. Real pain to get the filter mounting back in. I ran the pump until I heard the return line flushing back into the tank. Will road test later to see if the filter was causing my poor running (no power) under load.

I did look in the hardware store and they do have a 5/16" compression junction which would let you cut the pipe and then join it again. That would need your OD on the pipe to be clean so the brass ring would compress on it tightly. They also have compression to NPT fittings which would let you install a hose barb if you decided to go with fuel hose.

[dmcman73]

Well I decided to do it the old way and leave the supply pipe as is. Just have to guess when torquing the top banjo bolt. Real pain to get the filter mounting back in. I ran the pump until I heard the return line flushing back into the tank. Will road test later to see if the filter was causing my poor running (no power) under load.

I did look in the hardware store and they do have a 5/16" compression junction which would let you cut the pipe and then join it again. That would need your OD on the pipe to be clean so the brass ring would compress on it tightly. They also have compression to NPT fittings which would let you install a hose barb if you decided to go with fuel hose.

No power under load? Did you check for vacuum leaks?

[Bitsyncmaster]

No power under load? Did you check for vacuum leaks?

I've had the problem cold engine for a long time. Last drive I had it really bad even after it warmed up. So it happened pretty sudden. Will idle and accelerate fine not in gear so was just thinking about it and my fuel filter is about 16 years old. So that's my first guess.

[r00b]

I could never get my fuel filter off, I had to use a vice. I would have never been able to get it off otherwise, without damaging it. I really like quick connects so I used one of my banjo to quick connect on the top and a quick connect that threads into the bottom and points down. Now I just disconnect the old filter and move the fittings to the new filter.

6955969560

I was hoping to find a filter with the male quick connects built in but all I could find were rated up to 60 psi.

[Bitsyncmaster]

Well my problem was not the fuel filter. I changed the lambda and ignition ECU and I think the problem is still there but by then engine runs better since it's warmed up. I checked the dwell and it runs on the high side at idle but seems good (40 deg) when I hold high RPM. So I'm thinking it's something in the fuel distributor but I'm going to run a fuel pressure check after it cools down.

Problem showed up when I mounted my lambda ECU to the metal bracket. That is why I tested another lambda ECU. So I don't think the problem is caused by any thing I did.

[Helirich]

The fuel system in a Delorean is high pressure, higher than typical fuel injection systems. I would not recommend just slipping a hose onto a pipe without have a bead on the end.

There is another option. You can put just a slight flare on the end of the tube. It?s not as nice as a bead because the hose will not slide on as easy, but once you get it on and tighten a clamp, it can?t pull off. The key to this is make sure the tube end is debured good. I?ve done this (on other cars) with good results.

[Bitsyncmaster]

There is another option. You can put just a slight flare on the end of the tube. It?s not as nice as a bead because the hose will not slide on as easy, but once you get it on and tighten a clamp, it can?t pull off. The key to this is make sure the tube end is debured good. I?ve done this (on other cars) with good results.

I was thinking the same. I do have flaring tools. Not fun working up in that area not with a lift.

Another thought is to "glue" one of those compression rings onto the cut pipe. I guess a thick locktite would hold it. Can't solder it unless you can undo the other end of the pipe and blow it clean.

[Jonty]

I was thinking the same. I do have flaring tools. Not fun working up in that area not with a lift.

Another thought is to "glue" one of those compression rings onto the cut pipe. I guess a thick locktite would hold it. Can't solder it unless you can undo the other end of the pipe and blow it clean.

I?ve done a filter recently and due to the difficulty in getting the top banjo off I disconnected the fuel line at the distributor and feed it back down under the car and allow me to get the filter to spin enough to undo hard line. I could then take the filter out with the top banjo and fuel line attached. Anyway just an idea

[Bitsyncmaster]

Well my primary fuel pressure is 75 PSI, control pressure started at 28 PSI and rose to 50 PSI in a few minuets of running. So all looks good. I added fuel injector cleaner into my half tank of fuel. Running at idle it looks like the dwell is back to normal. I was getting 60 deg at idle before, now it's 45 deg at idle. Holding higher RPM it still reads 40 deg.

I can't road test with my fuel pressure gauge connected. So the real test will be later.

[Bitsyncmaster]

Well still has the problem. Seems a little less often but still can't drive it anywhere but around the neighborhood. All I can think of is a problem with fuel distributor. I guess I could do a flow test but since it's a random problem a good test will tell me nothing. Time to go EFI soon.

[mhanch]

So i was watching the Youtube video of Tyler Hoover when he bought his DeLorean - this sounds similar to what he was seeing which ended up being an issue with Fuel pickup when driving around. Maybe you have a issue at the pump or tank? Clogged baffle or something like that?

[Bitsyncmaster]

So i was watching the Youtube video of Tyler Hoover when he bought his DeLorean - this sounds similar to what he was seeing which ended up being an issue with Fuel pickup when driving around. Maybe you have a issue at the pump or tank? Clogged baffle or something like that?

Thanks for the suggestion. But I have the GM pump so no pickup hose or baffle. Just as a last resort, I'm going to replace the PPR-Orings. I did replace the larger one which had disintegrated but the small one looked good. I do note my rest pressure only holds for one hour now. It was holding for 3 hours last time I checked it many years ago.

[David T]

Check the timing, mechanical and vacuum advance. Do a smoke test to find any vacuum leaks. Make sure all of the vacuum hoses and vacuum systems are functioning correctly. Especially the one on the CPR. It does what an accelerator pump does on a carburetor.

[Bitsyncmaster]

I ran the six bottle flow test on my FD and nothing bad showed up. I watched the spay at all positions of the air flap. All looks good and even final flow from all that testing was very close to even amount from all six injectors. So now I don't think my FD is the problem.

Will have to think about it more. Engine runs great starting, idle and high RPM not in gear but under load road testing it feels like lack of fuel. I have the Tahoe fuel pump setup so it's not a tank pickup problem. Fuel pressure is 75 PSI primary and control pressure is 50 PSI on warmed up engine. What I'm thinking of doing is to wire up a fuel pressure gauge so I can monitor control pressure when driving.

It's really bad on the road so I can not drive it anywhere but around my neighborhood.

[Rich]

Will have to think about it more. Engine runs great starting, idle and high RPM not in gear but under load road testing it feels like lack of fuel.

..It's really bad on the road so I can not drive it anywhere but around my neighborhood.

Did you explore David’s t’shooting topics from post #17 yet? Results?

One suggestion to add to that list - a simple vac advance counter-test; disable the vac advance by disconnecting and plugging the hose from the vac solenoid to the vac diaphragm. Or just clamp the hose shut for the test. See whether the engine behaves differently or not. “No change” points to a vac advance system issue.

[Bitsyncmaster]

I put an OEM ignition ECU on and I think that fixed it. If that is the problem it may be the pickup coil or connection. Or I have a flaky connection in the ECU connector. I last checked another ECU when I first had the problem but that was also a GM modified unit.

I will need to due another test drive when the engine has sat overnight.

[Bitsyncmaster]

The rain finally stopped so I took the car on a test drive with OE ignition ECU. It ran good. Next I plugged in my spare GM ECU. It ran good. Last I removed the two ground wires attached to the metal mounting plate and plugged in the mounted GM ECU and it also ran good.

The OEM harness runs two ground wires into the ignition ECU. They are crimped to one pin in the ignition connector. One of those ground wires goes to a ring terminal and is normally screwed down on the idle ECU mounting screw. Both the OEM and my GM ignition ECUs do run ground to the ignition ECU mounting plate. So it's not good for electrical noise to have two ground connections like that. Ring terminal ground on the lambda ECU also makes a third ground to the metal plate. The lambda ECU has no connection to the metal box it mounts in.

So I remember some owners having problems using the GM ignition modules and I bet those needless grounds were causing problems. You can test just by removing those two black wire ring terminals from the metal plate (let them float).

So my metal mounting plate is grounded at one point by the mounted ignition ECU. The OEM harness runs a ground wire to one connector pin and the pickup ground (shielded wire) goes to another pin but the ECU connects those two signals.

[kings1527]

Funny you mentioned this job. I'm just getting ready to tackle mine for the third or fourth time since becoming an owner and I dread it every time for the reason you mentioned. My latest plan is this: take a flex head 17mm flare nut wrench so I can reach and leverage the top banjo on the filter and not have to mess with the lower portion of the filter at all, aside from spinning a new one on there.

Removal: remove top banjo. Remove bracket. Unscrew filter from elbow. Install in reverse. Of course, making sure to use secondary wrenches when needed to keep torque isolated and not twist anything that doesn't need to be twisted. Looking to do this sooner than later so I'll report back.

https://www.amazon.com/dp/B0014ZYZEC/?coliid=I6ERTFHH1TJAI&colid=28YS7B0F0QAC0&ref_=list_c_wl_lv_ov_lig_dp_it&th=1

[Rich]

Also, there?s the DMCH recommended method (http://support.delorean.com/kb/a62/fuel-filter.aspx) for fuel filter replacement.

[kings1527]

Also, there?s the DMCH recommended method (http://support.delorean.com/kb/a62/fuel-filter.aspx) for fuel filter replacement.

That method works great when the compression fitting actually separates.

[FLUX @88]

How often should the fuel filter be replaced on these cars? I replaced mine almost 2 years ago and roughly put 8k miles on.

[WHO1DMC]

How often should the fuel filter be replaced on these cars? I replaced mine almost 2 years ago and roughly put 8k miles on.

According to dmch 2 years or 15000 miles.
I have about 9 years 11000 miles on mine. But I'm going to put it on my fall to do list.



Dave B.

[Bitsyncmaster]

The rain finally stopped so I took the car on a test drive with OE ignition ECU. It ran good. Next I plugged in my spare GM ECU. It ran good. Last I removed the two ground wires attached to the metal mounting plate and plugged in the mounted GM ECU and it also ran good.

The OEM harness runs two ground wires into the ignition ECU. They are crimped to one pin in the ignition connector. One of those ground wires goes to a ring terminal and is normally screwed down on the idle ECU mounting screw. Both the OEM and my GM ignition ECUs do run ground to the ignition ECU mounting plate. So it's not good for electrical noise to have two ground connections like that. Ring terminal ground on the lambda ECU also makes a third ground to the metal plate. The lambda ECU has no connection to the metal box it mounts in.

So I remember some owners having problems using the GM ignition modules and I bet those needless grounds were causing problems. You can test just by removing those two black wire ring terminals from the metal plate (let them float).

So my metal mounting plate is grounded at one point by the mounted ignition ECU. The OEM harness runs a ground wire to one connector pin and the pickup ground (shielded wire) goes to another pin but the ECU connects those two signals.

Well I knew it to good to be true. The D is back to very bad running on the road. I guess that ground wire change was just due to my problem intermittent and it ran good doing some tests. Car is now staying in the garage till I get EFI.

[FLUX @88]

According to dmch 2 years or 15000 miles.
I have about 9 years 11000 miles on mine. But I'm going to put it on my fall to do list.



Dave B.

thanks for reply

[David T]

Mileage has nothing to do with filter changes for most of us anymore. Originally all of the maintenance schedule was based on using the car regularly and putting roughly 10,000 miles per year on the odometer. If you figure 20 MPG that comes out to about 500 gallons of fuel. A lot of things have changed about fuel. It is a much more filtered product because almost all cars are now fuel injected and therefore much less tolerant of dirt. Also because of the alcohol content more contaminants will dissolve and not get caught by a filter. Time doesn't matter all that much to a filter, a filter only catches what dirt goes through it so if less fuel goes through it, it will stay cleaner longer. There is a filter in the fuel tank too but it catches the larger size particles to protect the pump. The biggest problem is phase separation of the fuel. That happens if you don't use the car and the fuel gets stale. That can happen in as little as 6 months. If you don't use the car the fuel should be drained out of it. If the car sits for an extended period of time with fuel (especially if it has Ethanol in it!) the fuel system should be drained and flushed and all of the filters replaced. As for a time interval to change the filter figure 1,000 miles a year for 10 years and you hit the 500 gallon mark. Using that metric change the filter every 10 years or 10,000 miles. Obviously you can extend that interval, changing that filter is a PITA.

[ssdelorean]

Mileage has nothing to do with filter changes for most of us anymore. Originally all of the maintenance schedule was based on using the car regularly and putting roughly 10,000 miles per year on the odometer. If you figure 20 MPG that comes out to about 500 gallons of fuel. A lot of things have changed about fuel. It is a much more filtered product because almost all cars are now fuel injected and therefore much less tolerant of dirt. Also because of the alcohol content more contaminants will dissolve and not get caught by a filter. Time doesn't matter all that much to a filter, a filter only catches what dirt goes through it so if less fuel goes through it, it will stay cleaner longer. There is a filter in the fuel tank too but it catches the larger size particles to protect the pump. The biggest problem is phase separation of the fuel. That happens if you don't use the car and the fuel gets stale. That can happen in as little as 6 months. If you don't use the car the fuel should be drained out of it. If the car sits for an extended period of time with fuel (especially if it has Ethanol in it!) the fuel system should be drained and flushed and all of the filters replaced. As for a time interval to change the filter figure 1,000 miles a year for 10 years and you hit the 500 gallon mark. Using that metric change the filter every 10 years or 10,000 miles. Obviously you can extend that interval, changing that filter is a PITA.


I'd have to check my records but I haven't changed my fuel filter in at least 10years. Well over due. But I put on between 9k - 13k miles a year. I still get 23-29mpg depending upon how I drive. So I guess it really would depend upon "if" any - and "what kind" of contaminants have gotten into your fuel lines to cause your filter to clog up. Yes, I'm over due. Yes it should be changed. But I would not be too concerned about it. If my car lasted this long, you going over a little bit should not matter much (unless your system was opened at some time changing lines or parts - or received contaminated fuel).

I also need to update my signature as I am up over 250k miles now.

[David T]

I'd have to check my records but I haven't changed my fuel filter in at least 10years. Well over due. But I put on between 9k - 13k miles a year. I still get 23-29mpg depending upon how I drive. So I guess it really would depend upon "if" any - and "what kind" of contaminants have gotten into your fuel lines to cause your filter to clog up. Yes, I'm over due. Yes it should be changed. But I would not be too concerned about it. If my car lasted this long, you going over a little bit should not matter much (unless your system was opened at some time changing lines or parts - or received contaminated fuel).

I also need to update my signature as I am up over 250k miles now.

Yes, you can consider yourself overdue but you are an exception because of all of the miles you do per year. BTW, one bad tank of gas can plug up everything but that is a rarity these days. More common to have a car parked (not stored) and years later the fuel has turned into shoe polish and you have to scrape it out of the tank. Today's fuel has all kinds of additives and cleaners in it so don't get too worried about changing the filter. Before you do the filter consider using a fuel system cleaner. I like Techron. Add it to a full tank of fresh gas and use it all the way down to Empty. Refill with fresh gas and then change the filter. That way you will have broken up and flushed out any deposits and trapped them in the filter that you will be changing.