Anyone having trouble with Mallory 4309 fuel pressure regulator?

I always get weird readings. It's been installed 3 years now, but I've never gotten a consistent fp reading. Sometimes it reads 2psi, sometimes it reads 10+ psi. I adjust to 5psi, and 2 hours later it's changed again.

I have a nice Summit fp guage with the oily stuff inside to keep the needle from vibrating. But I thought, maybe the guage - so I got a Mr. Gasket guage today. The old guage read 6psi, installed new guage, it reads 18psi. I tried adjusting the reg, and I can't get below 8psi on the new guage before the adjuster comes all the way out of the regulator. The whole time, the car is running, and no change in the engine at all during these adjustments.

So, I thought maybe the Mallory 4309 - I had another laying around, so I swapped regs - same thing - can't adjust below 8psi or the adjuster falls out. No matter where it's adjusted, car runs with no noticeable engine changes.

If I adjust to higher pressures, at about 18psi on the Mr. Gasket guage, the regulator starts a ticking noise, and the guage bounces from 10 to 20psi on each "tick" sound.

Anyone have a clue what any of this means?

I'd try a rebuild kit for the Mallory 4309 - but this problem has existed ever since the day I installed the brand new Mallory unit, so I don't think it's a bad diaphram in the Mallory unless it was bad from day 1.

What started this? Sometimes my car bogs instead of accellerating. Sometimes when I try to start it, it needs a hint of gas pedal - like you'd think a carbed car would want. Other times it's like it's flooded and takes a minute to start - if I apply any pedal these times it won't start. So I started taking notice of fuel pressure readings.

Also, I have no tunability in the carb. The only thing that makes any difference in idling is when the screws are all the way in (kills motor), or all the way out (again kills motor) - no adjustment anywhere in the middle has any effect.

Edelbrock 1405 carb, mild 350, mild cam, TBI in-tank pump.

Any help greatly appreciated.

 

i've been having the same issue when i went to carb and kept the tpi in tank pump. the needle would spike and bounce. been running that way for 3 years with no problems. i believe it's because the tpi pump is trying to push out 40 something pounds or what ever it is of fuel pressure and it's being regulated down to like 5 lbs

 

Mine bounces too...but not nearly as bad as you're describing. I think the fuel return line size has a lot to do with it. Are you still using the stock 5/16" or 3/8" return line? The Mallory directions recommend a -8AN line, which is a good bit bigger. I have my screw adjusted all the way out just to get the pressure down to 6-7psi. I plan on putting a bigger return line in soon.

 

Mine did the same thing I wasnt impressed with it at all. Leaked out the top and every fuel hole. The pressure would bouce all over like you decribed never got it fixed. I am switching back to TPI so mine is going away

 

Im good freinds with a ex GM tech who designed the IGN systems for our GM cars, he worked side by side with Doug Roe who designed the Qjet for GM.

And this is what he say about them as a company

Press each index finger at the corners of your eyes, hook your pinkies into the corners of your mouth and then pull them apart,
while saying "Mallory me Chineese"

semi racist but not against the people but their quality of parts.

 

That goes double for Mr. Gasket. I haven't gotten anything of quality from them for many years (their "gold" gaskets one exception, which were replaced when I was able to get Fel Pro replacements). I almost burnt down my car with one of their Holley dual inlet fuel lines a couple of years ago.

I will never, ever again buy anything Mr. Gasket, especially anything that goes in the fuel system. I'd suggest getting that gauge out of there before you have an "incident".

 

At least with the Mr. Gasket guage, thus far I've been getting a consistent reading - somedays the Summit guge read 2, somedays it read 12. So at least now I think I at least have a consistent fuel pressure and not a daily changing making me fuel pressure.

And after further review of the Mallory instructions, it seems that the fuel pressure will never drop - the stock 5/16 return line is a restriction, causing pressure increase above advertised parameters. I called a few others today (Barry Grant, Aeromotive, Quick Fuel), they all state that if the return line is smaller than the feed line, the pressures will be higher than advertised.

What would be the end result of installing another deadhead style regulator between the mallory and the carb? I really only need to get fuel pressure down another 2psi maybe - think that small extra 2psi dead-regulated pressure change would kill the Mallory 4309 or the in-tank pump?

 

I've been having the same issues with mine ever since I put it in for the 350 swap 2 winters ago. I still have the OEM V6 fuel pump and the pressure doesn't seem to stay steady and I've been having all kinds of leaking issues with my carb. Fuel leaks from the needle/seat assemblies, fuel bowls and transfer tube as well as a fuel drip from the secondary boosters. Its a Holley 600CFM VS carb. I thought going to a TBI fuel pump would help since it outputs at a lower pressure(12-15psi vs 65-70psi), but if you're still having the same issues I am then I guess its not worth it. I have noticed that my return line will actually bounce around like a 2-year-old that has to pee from the excess pressure being returned to the tank so that would seem to confirm the line is too small. I'm still running the stock 3/8" feed and 5/16" return lines.

 

Id just stop using the intake pump, put a $30 electric one rated for a carb in the fuel filter location and be done with with it.

It will have no problem what so ever sucking the fuel through the intake pump.

Then no need to regulate the intake pump that puts out 10 times more then you need.

 

OK - I give up. I just went out for a ride just to see. For 2 days I've started the car in the driveway probably over 100 times (also been tracing a starting wire issue), drove it 15 ft forward and backwards several times (to get off the incline of my driveway), and each time I've had a consistent 7psi setting - too much, but not by much. Now, after a 4 block drive, I pull over, pop the hood, and fuel pressure is now at 12psi, and there's no adjustment left except higher. So I give up.

How can the pump run with engine on, engine off, gunning the gas as well as a plain 800rpm idle, off and on for hours each day for 2 days, with a consistent 7psi - and then after 4 blocks it's now 12? I don't get it! I'm madder than a hornet! Just once in my life I'd like something to work the way that it's supposed to, but I guess that's asking too much!

I'm not sure where anyone ever got the idea that you could carb a 3rd gen F body using the in-tank pump and ANY regulator without changing fuel line sizes - it just ain't happening. Sure it will work, and the car will drive - but there's going to be too much fuel pressure, period. This causes alot of problems for a carb, and it's not worth the attempt - sorry I followed suit and tried it myself, I should have known better.

Other than being pissed, I'm not sure what I'm going to do.

 

read my post above, use the stock intake pump wireing to power it and in id sayless then an hr all your troubles are gone for good.

 

But everyone says you'll not draw enough fuel through the dead pump, and if you do, you'll kill a rail mounted carb pump trying to.

 

I agree with Gumby. But, I will qualify this by saying that at some point you would do well to drop the tank, remove the stock pump. Replace it with a pick up tube. Then install a good pump like one of Holley's electric units with a good filter before the pump. This will assure you of long term trouble free operation. When installing the electric pump, I would keep your Mallory regulator. It bypasses fuel back to the tank and will prevent vapor lock. Also, 2psi is a little low. 4-7 is better.

 

I did think of one thing I did today that could have bumped the pressure up more - since the return line is a 5/16 size, and I was having such a hard time getting that 5/16 factoru hose to push over the 3/8 barb I had on the regulator, I swapped for a 5/16 hose barb. The only one I could find was a 1/4 NPT thread, so I had to use a 1/4 NPT to 3/8 NPT adapter to install the 5/16 barb into the 4309.

Wonder if I got a fitting to attach to the stock return line at the frame rail that had 3/8 hose instead of the factory fitting/hose piece that uses the 5/16 hose? Maybe just maybe that would relieve enough pressure?

 

nope, done it, and anyone who has changed a fuel filter or broke a fuel line, like I did sat, you will see the gas will siphon out of the tank like water out of a garden hose creating an instant lake of gas, which is more then enough flow for a carb.

I think that myth is when someone waits till the intake pump is fried dead, then tries to run an external FI fuel pump, and then Id say no, its not gonna suck the fuel needed for a FI system through a burnt out pump.


Though yes when you got time, you can drop it and do it all over but in about an hr of work, you can be back on the road n do it at your leasure.

 

And what he says.....

But $20-$30 will get you an electric pump at any corner auto store that will do that just fine and get you on the road and smiling again pretty quick.

Id kinda agree on your return line problem but the only fix id see is to drop the tank and re-plumb it all for new larger line. and id probably go with 1/2in for both as with carb ya don't need allot of PSI but if ya build it bigger later, you will want more volume.

 

I've got 3 installs with the Mallory 4309 under my belt now and all 3 work flawlessly. Two used the stock TBI in-tank pump and now my 3rd install is in my 454SS big block truck using a Walbro 255 in-tank pump (high pressure, high volume pump). All installs still use the stock 3/8" feed and 5/16" return lines with no issues and almost no change in fuel pressure under any conditions.

If the stock 5/16" return line was a restriction you would expect to see "pressure creep" at idle when fuel demand at the engine is lowest. But it doesn't creep up at idle and it doesn't fall off at WOT in the upper RPMs, so the lines are adequate. At least adequate for feeding a ~550HP big block with a fairly stout in-tank pump.

If there is a restriction somewhere in the system the readings can get erratic, especially if it's on the return side.

I would wonder about the in-line pump drawing through a dead in-tank pump possibly causing issues, or cavitating under the strain of the draw.

Another thought- You DID leave the boost-reference port on the regulator OPEN, right? NOT hooked to vacuum and NOT capped, right?

Out of the box the 4309 will supply about 4 PSI. You can back it down to about 2 PSI before the screw basically falls out. It will go as high as ~15 PSI before running out of adjustment and requiring a different spring to be installed to achieve any higher pressures.

 

Nothing connected to boost reference.

Out of the box, the 4309 will provide an advertised 3-12psi, but if you read the install directions, it clearly states that for 16-20ft of distance, at minimum there must be a 3/8 return line, where we have 5/16. Talked to their techs, smaller return than feed line will create an increase in pressure that cannot be adjusted out.

I tested today - connecting a 3/8 line to the return port on the 4309 that ran into a gas can -I could adjust to almost 0psi with this 3/8 return line to a gas can, so the issue is definitely the 5/16 line. I'm amazed anyone else has had any success - the truck would have a shorter fuel line run, shorter run means smaller feed and return line can be used (according to Mallory) with success, so that makes sense.

There is no in-line yet, just the in-tank pump - I might try an inline pump and make the in-tank pump dead - guess I only have $30 to lose.

The only time I ever saw 2psi was with the Summit fuel pressure guage I first had, and it was always giving weird readings, changing with every turn of the key. With either of the other guages I've tried (Mr Gasket and Spectre), I've not seen below 7psi. I'm sure it was the Summit guage.

Edelbrock says that engine cutting off on a sharp turn is too high fuel pressure - they state that anything over 5.5psi is too much, and that should never have 6psi+ or problems will happen (like the cornering cut-off problem which I have).

I've not had any problems until now - but then again I wasn't "driving" the car until lately. I drove it alot, but was always just slowly cruising, and normal 'granny' driving. It's been in and out of the paint shop for almost 2 years, and I've spent alot of time with suspension and restoration. Lately, I just started really getting into it hard, as everything else is mostly done now (done enough to start to enjoy driving it instead of trips to the paint shop, road testing suspension, etc.) - I always knew there were tuning issues that needed tended to, but just never got there until now.

I appreciate all the replies! It's frustrating - my fault mostly for not getting these issues tended to 3 years ago - but like I said it runs, and pretty good most of the time (unless I start having fun, which was the point in swapping in the 350 carb in the first place!). I just need to work out the bugs so I can hit the gas with confidence on occasion

 

Even with the 3 line engine mount fuel pump with the built in regulator/return; my 80 350 V8 wagon still does that. [big AC cars had that stock and a mechincal stock pump should not be to much psi]

I think its float bind, fuel rushes to one side and tries to **** the float sideways and it sticks for a sec, if it was to much PSI it should over run it and belch from being rich id say. [Like if my manaul choke I got on it is on to much when I give it gas, its way noticable, but no it just stumbles around a turn like fuel loss, just a dead spot for a sec.]

But thats just a good guess. Would like to solve it myself though.

 

Enough to feed a V6, maybe.

I've never seen a $30 in-line pump that was worth the time to install it.

 

Your personal beef's with the V6 cars are not part of the subject [yes we know you hate them/us ], and it was all on V8 carb cars.
And they worked flawless.

But again its only to get him back on the road, then do it all over from tank to carb better when he has the time, energy or money.

 

It's not a personal beef with V6 cars. I have no personal beef with V6 cars.

The OP has a V8. You were relating personal experience. You didn't state (until now) what engine was being fed by the set-up you proposed, and your user info indicates you have a V6. 2+2 would conclude you were talking about pulling through an in-op in-tank electric pump to feed a V6 engine.

The instances of TGO members having problems with trying to feed a V8 engine by pulling through an in-op in-tank electric far out number those who have not had problems. The problems multiply when the V8 is performance upgraded.

Newbie, I'll say again, get rid of the Mr. Gasket gauge. I had one that read consistently as well - consistently wrong. If you really had 18 psi going to the carb, you'd have flood city - no carb I know can handle that kind of inlet pressure. Get an Auto Meter or a similar quality gauge so you can trust what it's reading.

 

Well, before I went off the deep end, I tried one more 'configuration' of what I had already. And it WORKED!!!

I moved the Mallory 4309 to the pass side of engine bay. I extended the return line with 3/8 fuel injection hose with a 5/16 hose barb with an adapter to 3/8 hose barb, the 5/16 barb goes into the stock return hose, then the adapter to 3/8, then the 3/8 injection hose to the reg on pass side. Connected the rest as usual to the carb, and for whatever reason, I can now adjust down to 3psi.

But I'm not sure that really solved anything. I cut another 3/4in off the factory return hose end to have a clean start. Later, when I picked it up to discard, I noticed something inside - looks like when I tried shoving a 3/8 barb into that 5/16 hose, the brass barb end was sharp enough to make a cut inside the hose, and there was a "flap" of rubber in there. I never saw it before because gas was coming out of it (I was on an incline) so I couldn't see anything in there before.

So it was probably that stupid flap of rubber creating a restriction this entire time! I feel kinda stupid for all this trouble - but then again, I doubt anyone else would have seen it either - I'd never guessed that the brass barb would have been sharp enough to cut the inside of the fuel line without having cut my finger off first!

I appreciate everyone's help and ideas greatly. I was getting so frustrated that it has worked for many others, yet not for myself (I have that kind of bad luck usually).

It always ends up being something stupid doesn't it?

 

So a 5/16 return is adequate?

 

Always seemed to be for everyone else, and now it seems to be for me too

 

Oh sure, just blame me

 

Good call.