wstrohm

Our '94 FD had 90,200 miles on it in 2006 when I had to replace the "Fuel Pulsation Dampener" due to a fuel leak. Here it is in 2015, at 110,600 miles, and once again there is a fuel leak in the engine compartment. So I have to de-layer the onion once again to find and fix the problem. Of course it could be a hose or coupling, but...

I was 9 years younger then, and I am not looking forward to this job.

MattGold

iTrader: (108)

Save yourself some trouble... Consider deleting it:

FD3s Pulsation Damper Elimination

j9fd3s

iTrader: (3)

we used to see the damper leak, and then the primary injectors would follow. the injectors leak from the electrical connector, and not the o rings, so you unplug them, and pressurize the fuel system.

it is also possible that its the regulator, although when those go the car usually runs BAD

wstrohm

Thanks to both of you for the advice. I visited the Banzai website and printed the instructions for eliminating the FPD. The instructions seemed to imply that if I did that, I needed to replace the stock FPR with an Aeromotive unit. Is that required (assuming the FPD is the problem)?

This sounds like a test rather than a fix. Is that right? If so, what is the fix for leaking electrical connectors?

IRPerformance

iTrader: (41)

No. The only downside I've noticed is a stock car on a stock ecu will have a slightly less than smooth idle without the damper. I've run cars like that for years with no adverse effects.

DaleClark

iTrader: (55)

It's all speculation until you find where the leak is coming from. Could be a pinhole in one of the fuel lines or something.

Usually if you just pull the upper intake manifold and pressurize the fuel system you can find the leak pretty quickly.

I'm glad you're taking steps to fix it instead of just ignoring it .

Dale

silverTRD

iTrader: (37)

People ignore fuel leaks? Wait...stupid question

Sgtblue

iTrader: (16)

Just curious...any fuel mods done to the car?

ptrhahn

iTrader: (9)

Would be pretty awesome if someone made a bolt-in FPD barbed hose (or AN) fitting that fit the FPD flange.

wstrohm

Thanks again for all your responses. There was a fuel recall many moons ago... don't remember exactly when; it was done at a Mazda dealer. I did delete the fan recall and went with Dale Clark's recommendation of trading the temp sensor for the FC unit. Even though the pre-cat has been replaced with a wrapped downpipe and the coolant temps are lower, it still gets quite hot under the hood. But I don't know whether under-hood heat is degrading the fuel system hoses, or the FPD.

I have to buy some parts before I begin this task. (Gaskets, O-rings, etc.) Fortunately we have another car, and having this one down for a while is not a problem in itself. If it is the FPD, I will probably delete it per Banzai's instructions rather than buy another new one. If it is the primary injector electrical connectors leaking, not sure what to do about that.

@ptrhahn: Yes, I would buy one today!!

j9fd3s

iTrader: (3)

that is how you diagnose them, the fix is to replace the injectors

dgeesaman

iTrader: (7)

If it's the FPR, I have a new stock one that I picked up for only $50. It's yours if you're interested.

I agree with the others - it's hard to know what's going on under there until you get to see it. Hopefully you won't have many hours to get the UIM off and perform the fuel pressure/leak test.

wstrohm

The problem will be deeper than I can see at removal of the UIM. The rat's nest & wire harness, and the ACV valve will probably still obscure the leak location... I think I will have to remove those too. (If I remember correctly.)

Thank you for your offer!

wstrohm

I have a question about the fuel leak test. Assuming the UIM, rat's nest, and ACV valve have been removed, with the wire harness tied back so I can see the fuel rails etc, can I pressurize the fuel system just by temporarily connecting the battery, jumping the "F/P" terminal in the Diagnostic Connector to ground, and turning the ignition key to "ON?" Or is there a different, necessary or advisable way to do this test with all this other stuff disconnected?

Do I have to reconnect the injector electrical connectors, or can/should they remain disconnected?

Thanks for your help!

j9fd3s

iTrader: (3)

the f/p terminal bypasses the circuit opening relay, and thus with it jumped, the fuel pump will work with the key.

i'd remove as little as possible, upper intake and maybe ACV, and then jump f/p. if the leak isn't obvious, you get to dig deeper...

just to recap, the damper will leak externally, through the end of the diaphragm. the injectors will usually leak through the electrical pins, and the pressure regulator will usually leak into its vacuum hose*

don't rely on just your eyes, follow your nose too.

*when the regulator goes bad the car runs really bad, not only does fuel pressure do odd things, it also leaks fuel into the intake

Tom93R1

iTrader: (2)

Fuel injectors can also leak out o-rings, although that usually goes directly into the engine and if it's bad enough to drip will be coming from manifolds/downpipe area.

Do you just smell fuel or do you see it dripping on the floor?

wstrohm

Once again, thanks much for your replies. So far I have only removed the under shield, drained the radiator, removed all the intake air tubes, the air pump, and the alternator. Throttle body is loose, but I am having trouble unlocking the TPS electrical connector... harness wraps tightly right over the locking tab and I cannot press the tab far enough to unlock the connector. Have had this problem before...

FWIW, the car has run beautifully for the last 60K miles since I replaced the FPD the first time. There is no fuel on floor, and I still cannot see into the area since the UIM is still attached. Hopefully I will solve the TPS connector problem today and get the throttle body and UIM off. IIRC, I will still have to remove the rat's nest and pull the wire harness back to view the fuel rail area.

I did get a very strong raw fuel smell yesterday when centering the car in the garage (cold engine running), before putting it up on jack-stands.

wstrohm

Update... throttle body, UIM, coil assembly removed. Still can't see a thing in the fuel rail area. Proceeding to remove solenoid rack and (probably) ACV.

j9fd3s

iTrader: (3)

do the ACV first, leave the rack

wstrohm

@j9fd3s,

First, thanks for all your support. I was able today to see the fuel rail area and run the pressure test. (I did remove the rack first, and then the ACV... didn't read your post until just now.) The test showed one primary injector electrical connector leak... the one at the rear (rightmost in attached picture). The FPD and all fuel lines stayed dry. But as you can see in the attachment, there is a reddish discoloration on the fuel line at the left of the picture. No fuel came out there when the system was under pressure, though. I would like your opinion on whether that line should be replaced, and also whether I should buy two new primary injectors. If one leaks, does that mean the other is not far behind?

I have also noticed that the wiring harness (the one that plugs into the solenoid rack and many other places) is seriously deteriorated. It is extremely stiff and hard to move about. This car is 21 years old now, and it is the original harness. I'm thinking about replacing it while this deep into the engine compartment, but don't know how much extra effort is required. Any advice?

Once again, thanks much for everyone's input!

dgeesaman

iTrader: (7)

IMHO, the original harness should be changed in the near future. Either leave it disturbed as little as possible to get this job done, or take the whole thing out.

Pulling the harness is a significantly larger job than this. Nothing impossible but you'll spend some more hours and most of it hanging deep over the engine bay.

Sgtblue

iTrader: (16)

Speaking only from my experience, those injector connections are likely pretty brittle. I'd consider replacing those. Pig tails are available with new connectors.
With the engine at 110K, statistics say it'll end up coming out in not too may more miles anyway. I think I'd leave the harness be as much as possible now and do a comprehensive continuity check and re-wrap (or replacement w/new) then.

DaleClark

iTrader: (55)

Many times the stock harness just needs new tape and loom. The old tape is brittle and terrible, but the wiring underneath is OK. Sometimes some new connectors are required, I've gotten fuel injector connectors off Mazdas in the pick and pull junkyard, backed the pins out of the broken stockers, and put them into the new plastic.

They're worth saving if at all possible, they're expensive new and I imagine stock will run out at some point.

Also, that red mark is just paint or something, Mazda puts paint marks on parts to show orientation, or that they've been tested to spec or whatever.

Dale

j9fd3s

iTrader: (3)

yep, replace both injectors.

with the harness, removing the solenoid rack is the hard part, so its a couple more hours, but you're like half way. last one i bought was $1000, its a work of art, but not cheap. someone will buy your used harness. Mazda USA has 3 harnii right now, N3A1-18-05ZG

wstrohm

@j9fd3s,

Thanks again. My 1994 parts catalog lists the engine harness (Illustration #1) as part number N3A1-18-05ZE (alternate is N3A1-18-05ZF). is the "-05ZG" part functionally different or just an update (maybe from another supplier)?

Also considering replacing the harness Illustration #2 with P/N N3A3-18-05Z. Does this make sense?