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Marren Fuel Injection FPD Retrofit Writeup

Old 10-10-04, 03:53 PM
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Marren Fuel Injection FPD Retrofit Writeup

Marren Fuel Injection Fuel Pulsation Dampener Retrofit Writeup

Disclaimer:
This how-to should be considered a general guide. It applies specifically to 1986-1988 Non-turbo RX7s only. The 89-91s have their FPD integrated into the fuel rail, and Turbo IIs are different in regard to parts layout. Also, the fittings I've listed below could be changed around to suit your needs. I am not responsible for any damage to your car if things go wrong.

Summary:
The Fuel Pulsation Dampeners on our RX7s were not well designed to begin with. They are prone to leaking when they fail, leaking fuel onto the hot exhaust manifold, eventually resulting in a fire. Many RX7s have suffered engine fires--totaling them. While you could remove the FPD and replace it with a banjo bolt, this could cause problems with the fuel system. Bear in mind that the purpose of a fuel pulsation dampener is to even out the pulsations caused by the rapid opening and closing of the fuel injectors.

Marren's Fuel Pulsation Dampener:
This year, Marren Fuel Injection has come out with a new fuel pulsation dampener. Made of billet aluminum with an anodized red finish, this component offers at least two major advantages over the factory unit. First, and foremost, the entire part is enclosed. This means that if it fails, it won't leak. Second, the unit is rebuildable, meaning that the unit can be taken apart and the wear parts replaced; this will be the last fuel pulsation dampener you'll need to buy. The unit is about 2 1/2" in diameter, with a 3/8" NPT inlet on the bottom, and a 1/8" NPT schrader valve on the side for pressure readings. The latter can be replaced with a plug, fuel pressure sender or gauge if desired.

Another advantage to the installation is that the placement of the unit will be on the end of the secondary fuel rail. That means you won't have to pull the upper intake to remove the unit. All you have to do to remove it is to depressurize the system, remove the intake elbow, push the vent hose on the intake snorkel out of the way, remove the pressure gauge, sender or valve, and then unscrew the FPD and remove.

Cost: ~200 for all materials and outside labor (assuming you have the basic tools needed and farm out the cutting of the hose)

Parts and Materials needed:
1 Marren Fuel Pulsation Dampener
1 3/8" NPT to -6AN male/male adapter
1 -6 AN female tee fitting
1 -6 AN male/male coupler
2 -6 AN female hose fittings
1 foot of -6 AN stainless steel braided hose
1 12MM x 1.25" banjo bolt (or reuse the bolt with crush washers from the end of the primary fuel rail)
1 14MM x 1.5" metric to -6 AN adapter
Teflon tape
1 foot of convoluted tubing 3/8" I.D.

Optional:
1/8" NPT plug, Fuel pressure gauge or fuel pressure sender to replace schrader valve

Tools needed:
2 19MM wrenches for the fittings
1 21MM? wrench for the hex end on the new FPD
Tools required to remove upper intake manifold
Permanent marker (to mark SS hose for cutting)
Proper cutting tool for stainless steel braided hose

Optional:
AN wrench set -- if you're doing a lot of assembly, a proper set of tools will help, providing proper torque and it won't damage the finish
AN fitting vise -- to hold the hose with fitting in place for easier assembly
AN hose cutter -- obvious

Important:

Materials/parts:
My selection of the fittings was mainly based on logic and played by ear. There can be some flexibility in what adapters or fittings you can use. I wanted to accomplish the installation with a minimum of new parts and fabrication. If you already have a parallel system or aftermarket hoses/lines/fittings, then this write-up won't really apply as far as the actual installation goes (it still is a good idea to use one though). This may also be a good time to pull your fuel injectors and have them cleaned.

Tools:
Please note that you can use regular metric wrenches on aluminum fittings, but you will mar the finish and possibly damage the threads on the fittings if you torque them too much. Stainless steel braid is very difficult to cut, and if you try using ordinary cutting tools, you'll find it frustrating. You could also cause a lot of fraying, making it difficult to properly attach a fitting to the hose end--wrapping it in ducting or silicone tape will prevent this. If you don't have the right tools, have a shop do the cutting for you. You can do the assembly of the hose yourself, just be sure to review a how-to on making your own braided hoses. I will not go into detail on that here, except be sure to blow out the hose with compressed air after assembly (there will be particles left from cut braid and hose)

General issues:
When the FPD is finally installed, you may have three clearance issues, two minor and one potentially major: the A/C hard line, the left front brake line and the heater hose. The brake line can be bent a bit toward the passenger side, and the A/C should clear without problems--only when removing and installing the Upper intake might this be a problem. If you don't have A/C then that clearance issue is moot. Unfortunately, the heater hose presses against the tee and -6AN male/male fitting. I used a piece of convoluted tubing between the hose and fitting to protect both from rubbing through. You may also have to replace the vacuum line on the cruise control actuator with a longer one (an easy fix). You'll also notice that the FPD will be on at an angle. This doesn't affect operation of the gauge or the FPD itself.

However, once the hood is back on the car, it'll obscure the view of your mechanical gauge, so running a remote fuel pressure gauge is a better idea. Having driven the car, the brake line issue isn't an issue at all, and the heater hose isn't really a problem either. As for October 10, 2004, I have run this car over 624 miles with no problems--including any leaks.

Don't be surprised if there are fuel leaks. They can occur if:

A. You didn't use enough layers of teflon tape on the 3/8" NPT fitting or the 1/8" NPT fitting. Use tape only on the NPT fittings. One of the leaks I had came from the NPT part of the adapter.

B. You didn't sufficiently tighten the AN fittings.

Safety:
***WARNING, YOU ARE DEALING WITH A FLAMMABLE LIQUID!***
You are working with a high-pressure fuel delivery system. If you do not depressurize the system, fuel could spray out. Don't let it get into your eyes. Gasoline is a flammable liquid. Before working, be sure that you:

1. Wear safety glasses
2. Work in a well-lit and ventilated space
3. Have a fire extinguisher nearby
4. Make sure the engine is cool
5. Make sure the fuel system is depressurized
6. Make sure the battery is disconnected
7. Go slow and take your time

Remember it's not the liquid that is flammable, it's the fumes. Any spark or heat source could cause ignition. I cannot stress safety enough. If anything goes wrong, remember:

1. To not panic
2. To call 911
3. That it wasn't my fault you destroyed your car/property

Directions:

***REMEMBER, YOU ARE DEALING WITH A FLAMMABLE LIQUID, YOU CAN NEVER BE TOO CAREFUL! OBSERVE ALL SAFETY PRECAUTIONS!***

Disassembly (this is assuming you know some of the general procedures from the FSM).

1. Depressurize the fuel system by running the engine and disconnecting the fuel pump relay. Let the engine stall out on its own.

2. Disconnect the battery. Take it out of car if you want and place it in a dry cool place away from the car.

3. Drain the radiator (if you did the throttle body mod, this won't apply) enough to not have coolant spilling out of the throttle body when you pull the upper intake).

4. Remove the upper black plastic air inlet and intake elbow.

5. If equipped, disconnect the cruise control throttle cable and vacuum line and move it out of the way. Also disconnect the throttle cable.

6. Disconnect all wiring and hoses from the upper intake manifold (taking care to mark them as you go, one by one, so you can reassemble everything in proper order).

7. Remove the secondary fuel rail. Be sure to remove the fuel hoses, vacuum hose, and have rags handy to contain any fuel spillage. Put the secondary fuel rail aside for later.

8. Remove all bolts, check again for anything you missed, and pull off the upper intake manifold and throttle body as a unit.

Modifications:

This may be a good time to replace your fuel hoses, filter and clamps. Use correct fuel injection hose and clamps. Same goes with cleaning your fuel injectors.

1. Remove the old FPD from the primary fuel rail and discard. Keep the fitting that the hose attaches to.

2. Remove the banjo bolt and fitting with crush washers from the rear of the primary fuel rail. Keep the banjo bolt and crush washers.

3. Reinstall the banjo bolt and crush washers onto the front of the primary fuel rail. Be sure to tighten it (don't forget the crush washers) to prevent leaks.

4. Install the -6 AN to 12MM x 1.25" adapter onto the rear of the primary fuel rail (using the crush washer and tighten to prevent leaks)

5. On the secondary fuel rail:
A. Pull the banjo bolt and fitting off the rear of the rail
B. Install the new 14MM X 1.5" to -6 AN adapter with crush washer
C. Screw on the -6 AN tee fitting
D. On the new FPD, use teflon tape on the 3/8" NPT side and install the -6AN to 3/8" NPT adapter on the FPD, then screw the unit onto the tee fitting. Orient it to have the schrader valve of gauge sender/gauge facing toward the driver side (it'll be angled up toward you).
E. Screw the -6 Male/Male fitting onto the bottom of the tee
F. Temporary place the secondary fuel rail back on the upper intake

6. To make sure that you get the proper length of hose for the new fuel hose that will connect the primary fuel rail to the secondary:

A. Terminate one end of the hose with a Straight -6 AN fitting
B. Install the hose on the primary fuel rail (use the convoluted tubing to prevent the braid from scratching anything)
C. Put the upper intake back in
D. Route the hose to the -6 AN fitting at the bottom of the tee and mark the hose with the marker
E. Remove the upper intake
F. Cut the hose at its mark and install the other straight fitting (use compressed air to blow out any shavings, etc)
G. Reinstall the hose on the primary fuel rail, placing convoluted tubing around it to protect it from rubbing against anything nearby

7. Remove the secondary fuel rail you temporarily fitted from the upper intake.

8. Reinstall the upper intake manifold, connecting the new -6 AN hose to the inlet on the secondary fuel rail--you may want to connect the rail while it's not on the upper intake.

9. Reassemble in reverse order

10. Once everything appears to be in place, reconnect the battery.

11. Repressurize the fuel system--CHECK FOR LEAKS. If you have installed a fuel pressure gauge, you can check its reading on the FPD itself.

12. Start the engine--CHECK FOR LEAKS.

13. Provided everything is working to your satisfaction, and the engine is running properly, you are done.

14. Enjoy.
Old 10-10-04, 06:11 PM
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Old 10-10-04, 06:21 PM
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BTW, it's the right front brake line, not the left front.
Old 10-10-04, 09:05 PM
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One last addendum. The heater hose clearance issue mentioned. I pulled the convoluted tubing I used and noticed that the fitting was rubbing against the hose. While it's not a problem now, it'll eventually rub a hole through the hose and you'll lose coolant. There is a fix.

With a short length of wire or strapping, wrap it around the hose and pull the hose away from the fitting (just enough to clear it). I used an existing bracket mounting point as an anchor point to secure the wire.
Old 06-19-06, 01:01 PM
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tips

I did this retro fit this weekend and thought I would share my experience and some additional tips for the procedure. First off thanks to cluosborne for the great write-up.

Missing from the materials list is the 12mm x 1.25" to -6an adapter for the rear of the primary rail. It is mentioned in the instructions, but is missing from the materials list.

Here are the corresponding summit part numbers for those having problems locating them (I was unable to locate some parts by searching the web site, but they're there if you search by part number).

1 Marren Fuel Pulsation Dampener
1 3/8" NPT to -6AN male/male adapter : EAR-981666ERL (also found on the Marren site)
1 -6 AN female tee fitting : AER-FBM2174
1 -6 AN male/male coupler : EAR-981506ERL
2 -6 AN female hose fittings : EAR-800106ERL (also found on the Marren site)
1 foot of -6 AN stainless steel braided hose : EAR-303006ERL (this is 3 feet, the smallest I found. Marren has it available in 1 foot sections from their site)
1 12MM x 1.25" banjo bolt : EAR-997591ERL (this comes with new washers)
1 14MM x 1.5" metric to -6 AN adapter : EAR-9894DBHERL
Teflon tape
1 foot of convoluted tubing 3/8" I.D. : TAY-38360 (I got the blue color)

1 12MM x 1.25" metric to -6 AN adapter : EAR-991945ERL

the 12MM x 1.25" metric to -6 AN adapter is not a common size adapter, so when you take your car apart and realize it wasn't on the shopping list....you're not going to find it locally (unless you have a summit...maybe?...). I actually ended up having to re-tap the primary rail for 1/4 NPT and used a 1/4 NPT to -6 AN adapter.

I also suggest getting some vacuum hose from mazdatrix (http://mazdatrix.com/c-silhos.htm) 5-10 ft of the 3.5mm, I got 3 feet, and I found more cracked hose than I expected so I ran out. You'll have access and it's cheap, so you might as well.

Make sure you have a new gasket for the UIM and new seals fo the injectors (3 per injector: 1 solid black piece, one grooved black piece, and 1 O ring)

If you have the time, you may want to send your injectors in for cleaning while you're at it. I couldn't do this because of turnaround time.

Check your oil metering lines as well, there's a write-up on rebuilding them if you're interested.

I blocked of the EGR while I had access as well.

Now to the actual work:

the -6 AN tee fitting I got did not have the tapered edges inside to seal with the other -6 AN fittings, so I had to find another way. O rings seem to work pretty well, but I used copper washers where I could because I thought they would be a more permanent seal than the o rings.

I planned to measure the actual hose length but forgot. I estimate it was 10-11" based on what I had left. I used a dremel tool with a cutting wheel to cut the hose to length and it worked very well. I also used a small hose clamp to compress the end of the braid to aid in getting it into the fitting, I think it made it a little easier. The hose I ordered came with a nice instruction sheet for finishing the hoses.

The orientation of the tee can only go one way, the long edge (top of the "T") should be perpendicular to the ground with the marren FPD on top. I tried the other way, but the FPD ran right into the firewall.

Hope these tips help, this retrofit is a great idea to get rid of the old PD. Good luck.
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