Replaced engine bay lines - banjo / washer leaks

[Chris 16409]

Dave, if you are interested in Dave McKeen's RPM relay I sell compatible cores so you can keep your original as a spare. Let me know if you are interested. I'll send you a PM as wll.

[DaraSue]

Once "righty tighty" becomes "righty loosey", you'll now at what point to stop.

That's pretty much what the tech I talked to said. It may be worth noting that I'm a 5'3" 120-something lb female so I'm probably not turning the ratchet with the same force as a 200 lb male. IIRC it's usually taken less than 1/4 of an extra turn to get it tight so obviously don't crank the wrench like you're closing a fire hydrant.

[DMC-Dave]

Thanks for the suggestions everyone. I only have time to work on my vehicle on the weekends, so progress is a little slow.

One correction; earlier I mentioned the original/new M8 bolts were the same length, but that is not the case! I should have measured instead of just eyeballing; lining them up opposite each other clearly shows this length difference (photo). The DPI bolts are 1mm longer according to my calipers, so bottoming out could be the issue?

I tried Dave’s suggestion of omitting one washer to test this, and for the WUR bolts at least, it does not appear to be bottoming out. I do wonder about the injectors now though that Jonathan mentioned it, which I haven’t yet tested and will probably need to revisit. It was also suggested that rusted / damaged threads at the bottom of the WUR might cause bottoming out; I used an endoscope down the hole and the threads seem OK.

I did receive the new washers from DMCH and I spent some more time sanding / cleaning surfaces, and trying evaporust. Installed again and torqued to max and tested; I thought I had it! But..after a few mins under pressure I started to get fuel weeping from the same spots (plus a few new; ostensibly now that the system achieves higher pressure). One step forward two steps back. Over torqued them by about 1/8th to 1/4th turn (as much as I dared) and tested again, but still weeping.

I wonder if lubricating the banjo threads might allow higher tensions on the bolts to be achieved, while lowering torsional stresses that might otherwise shear the bolts. Although I realize lubricated torque specs are lower, not sure by how much on these bolts, has anyone tried this?

Damn, this has become very frustrating. I’m not a mechanic but I’ve done my share home garage work; tire rotations, oil changes, tune ups, etc. all no problem for me. I didn’t expect this job to be kicking my arse so. This weekend I’ll try another round using the old bolts in the problem areas. I’m cleaning them up now.

If that doesn’t work I may need to admit defeat and try to find some place to tow it to and have the pros take a crack at it. I’m about 12 weekends into this job, when I expected only 2 or 3; I’ve lost most if not all of the driving season to it at this point, I should have just driven the car and not worried about it until next spring. Gah!

[DMC-Dave]

Has anyone used or heard anything about Silver Arrow service in Hudson NH?

https://silverarrowservice.com/delorean-2/

Website indicates experience with PRV (although it's kind of hidden on their site).

[Rich]

One correction; earlier I mentioned the original/new M8 bolts were the same length, but that is not the case! I should have measured instead of just eyeballing; lining them up opposite each other clearly shows this length difference (photo). The DPI bolts are 1mm longer according to my calipers, so bottoming out could be the issue?

I wonder if lubricating the banjo threads might allow higher tensions on the bolts to be achieved, while lowering torsional stresses that might otherwise shear the bolts. Although I realize lubricated torque specs are lower, not sure by how much on these bolts, has anyone tried this?

Go back to your original bolts since you know they weren't bottoming out. Aside from wanting a "new bolt look" there's seldom a need to replace them unless they had stripped threads. Your photo shows good threads.

Again, you'll want to use a new pair of factory-spec washers each time you torque down one of these fittings. While it's possible for them to be reused they don't always seal well. At this point you want no risk.

Further notes:

Do NOT lube the banjo bolt threads.

Check to be sure your torque wrench is set correctly. Some of them have vernier marks that are hard to read; you can be off one way or the other by a whole turn.

Two washers per fitting - be sure you have one washer above AND one washer below each banjo fitting as you fit the bolt to the fitting. You probably noticed this when you took it apart.

Closely inspect each side of any "leaking" banjo fittings - both faces must be free of any nicks or scratches. Don't used damaged ones.

[rjd2]

I know that they are a bit pricey, but maybe a year or two ago I switched from torque wrenches to a digital torque meter, and never looked back. I have used it on every significant fastener in an engine bay since. I just found the traditional clicking mechanical wrenches to be too prone to user error. So instead of it clicking, you read the meter, and stop where you want. you can tighten to a level of accuracy that's pretty amazing.

https://www.summitracing.com/parts/b...hoCyhcQAvD_BwE

Also, I don't know if this would help, but I often use aluminum crush washers in lieu of copper. Casey Putch from Genius Garage suggested them over copper once, and I have found them to be just as good. I have also reused copper washers multiple times, but if you are smashing the hell out of them then maybe they can leak?

The fact you are getting leaks on a number of connections would lead me to believe there's a systemic issue-tool, part, or otherwise. Stick with it. You'll get it. I havent done it on a DMC just yet, but on other vehicles I have bridged the pins of the fuel pump relay to get it to run. It's a nice way to check for pressure without having to run the engine. Just a thought, if it stresses you out to run the engine just to find leaks.

[Bitsyncmaster]

Never had any leaking problems with my injection parts but I did have a leaking otterstat (screw in type) which seals with a copper crush washer. To get that to seal I used two crush washers instead of one. I suspect the otterstat pipe did not have enough chamfer and the threads blocked it from pulling down enough.

[Chris 16409]

Never had any leaking problems with my injection parts but I did have a leaking otterstat (screw in type) which seals with a copper crush washer. To get that to seal I used two crush washers instead of one. I suspect the otterstat pipe did not have enough chamfer and the threads blocked it from pulling down enough.

Hey Dave I had to use Teflon tape to get it to seal. The included washer doesn’t do much.

[Chris 16409]

If you get the new banjo bolts from D-Go you must get their thicker M8 washers to use them on the injectors. The bolts are longer than stock. I don’t recommend changing bolts either unless they are corroded or damaged. You should not have to sand the washers down or any of that. I’ve changed out about a dozen fuel lines for owners and have never faced the issues you describe.

[Jonathan]

Something else I thought of that the OP might want to double check is the thickness of the ends of the new fuel lines when compared to the originals. If you are making a sandwich at each connection of one hoop on the end of the line together with two copper washers and being concerned if the bolts are now too long (or too short), that line hoop thickness will be important too. If you take one of your old ones and just put it side by side with the corresponding new one, you should be able to tell pretty quickly if they are the same thickness or not.

For the longer bolts bottoming out, you can also take any of those locations and just gently thread in the bolt with nothing attached to it. Stop when it gets bottomed out and measure the distance of what is now left between the top edge of what you are connecting to and the bottom edge of the head of the bolt. If that distance leftover is greater than the thickness of two washers plus the thickness of the hoop, you're going to get leaks.