fuel pump regulator

[racerx]

I have a 32/36 weber on L-18, measured fuel pressure with in line gauge and pressure is 4 lbs at idle and then when I get on the engine it's like 5 lbs. Read somewhere that 32/36 ran best at 2.5-3 lbs. If so do you guys run a fuel pump regulator with stock fuel pump that I got from Oreilly, use to be Kragens. Thanks, RacerX

[Z-train]

I use a retrun line with a metered hole.

[benzo]

never used a 32/36 but I am using a holley regulator with stock pump for my mikuni's and it works so far. I was at 6 psi stock and took it down to 3 psi and the car was a bit better running wise. I got my regulator from Summit.

[banzai510(hainz)]

most time a regulator is need with a electric fuel pump as most are about 7psi

there are others that are lower pressure and self regulated like the Walbro ones that I seen you can adjust it.

 

the stock 510 pump(koyosan or nikki) should be fine with a DGV or sidedrafts, no reg needed.

 

 

I dont run them. Only on my yellow car I got a electric pump and a Puralator dial type regualtor

[racerx]

Is that Puralator, as noted by Hainza, a good one.

[banzai510(hainz)]

seems to work. but was on there from PreviousOwner

[racerx]

okay will look into it..can you do me a big flavor and see what model it is..thanks.

[Z-train]

most time a regulator is need with a electric fuel pump as most are about 7psi

there are others that are lower pressure and self regulated like the Walbro ones that I seen you can adjust it.

 

the stock 510 pump(koyosan or nikki) should be fine with a DGV or sidedrafts, no reg needed.

 

 

I dont run them. Only on my yellow car I got a electric pump and a Puralator dial type regualtor

Starting in 78(al least)all trucks had regulators "of sorts",meaning a return line with a metered hole.

[ggzilla]

All stock mechanical fuel pumps are regulated, the same way an external regulator works, by a spring, except they are non-adjustable. The great things about Datsun fuel pumps are 1) they are the right pressure for Webers and 2) they are high flow, so work great with sidedrafts and twice stock HP.

[racerx]

Perhaps you did not read previous post, the beginning, I hooked up a fuel pressure gauge on the stock, Oreilly (Kragens), fuel pump and reading was 4 lbs at idle and when I press on the gas pedal and rpm went then the fuel pressure went to 5 lbs. Been reading that webers like 2.5 -3 lbs. And I called Pierce manifolds and they said not mroe than 3.5 or else our car will not idle consistently. Thereby will have a hard time adjusting or carbon build up will take place in the plugs....

[ggzilla]

Yes i read that. The Oreillys pump is out of spec. A Datsun fuel pump for 1974 L18 should be 3.0 to 3.8 psi. 4 lbs is defective. Howver if you put a regulator on it, then it will work OK.

 

Weber specifies 2.5 to 3.0 lbs pressure, but as long as it is consistent 3.5 or 3.8 is fine. Varying pressure is bad and leads to varying idle and mixture. Webers from the 1960s would have seat problems with more than 3 psi, but the needle & seats they've been using the last 30 years will do 3.8 psi no problem.

[Sealik]

Perhaps you did not read previous post, the beginning, I hooked up a fuel pressure gauge on the stock, Oreilly (Kragens), fuel pump and reading was 4 lbs at idle and when I press on the gas pedal and rpm went then the fuel pressure went to 5 lbs. Been reading that webers like 2.5 -3 lbs. And I called Pierce manifolds and they said not mroe than 3.5 or else our car will not idle consistently. Thereby will have a hard time adjusting or carbon build up will take place in the plugs....

 

 

You didn't mention if you are utilizing a fuel return line....should be considered if not.

There are various lbs of pressure suggested by Weber suppliers...anywhere from 2.5 - 4 lbs.....all relative to a return line...... and mechanical or electric pump....etc...etc

Most Webers will run fine without a regulator....as long as a return line is functional.

I can dial my regulator in at 2.5 lb.....or 4 lb with the electric pump...basically no diff...because there is no 'restriction' in the line....the fuel is circulating to the carb and back to the tank

[ggzilla]

Doesn't matter if you have a return line or not. 3 psi is still 3 psi with or without return line.

 

For EFI the return line is critical to regulation, because that's how most EFI fuel regulators work, by dumping excess out the return line. But a mechanical fuel pump regulation doesn't work that way, instead it stops drawing fuel.

[racerx]

Will it matter if I have L16 or L18 fuel pump from Oreilly...they look the same but part number is different.

[banzai510(hainz)]

part number is differnet cause the inlet out lets are different.

510/521 use one type and L18 used a different type on the trucks. Cant be certain on the other models but they are more or less the same diaphrame tyep pump sand once the fuel is in the carb the pump should go limp anyways.

 

I think the common aftermarket is a blackstone brand with the gold stamped cap. They seem to work last time I had one. Just look cheap but I have to say they dont have a breathe hole and the two pivot stubs on the side which famously leak oil on the Koyosans/Nikkis. But I like the looks of the stock mechanicals.

[Z-train]

1)Doesn't matter if you have a return line or not. 3 psi is still 3 psi with or without return line.

 

2)For EFI the return line is critical to regulation, because that's how most EFI fuel regulators work, by dumping excess out the return line. But a mechanical fuel pump regulation doesn't work that way, instead it stops drawing fuel.

1)This is not true.Factory 620's have a regulated return line and the orifice in the line determines how much FP reaches the carb.It's a PITA but you can change fuel pressure by changing the size of the return line orifice.

2)Correct.

[ggzilla]

Thanks for that information, I learned something new today.

[Z-train]

Time permiting,i'll put up a pic.

[racerx]

The fuel pump I got from Oreilly's is made by Airtex..the L16 and the L18 type looks the same but inlet is on other side, weight is diffrent, the Max. pressure/min. pressure (PSI) is the same but the GPH or gallons per hour is different - from Autozone specs of fuel pump. The housing looks basically the same but the inside is different. Still having the issue..of idle rpm, after a minute or so, goes down from 850 to 500 rpm. I will try a fuel regulator. I'm hoping my carb (32/36) is not going south, it is only 2 years old from weber direct. I checked everything out: vacuum, dwell, distributor, plugs, plug wires, dist. cap, rotor, adjusted carb, checked coil's primary and secondary okay w/in specs. Not giving up..this is the fun part...

[pocket rocket]

check the advance in your distributor - make sure it is lubricated & not hangining up.

check throttle linkage - make sure it is well lubricated, operates smoothly and doesn't hang up, lube throttle shaft (& make sure it is not bent), make sure throttle return spring is located correctly and does its job as it should.

 

As for the fuel pump, pressure is directly related to flow.

 

However, it would seem odd that a slight increase in fuel pressure would cause the problem that you describe, especially when you said it eventually idles down from 850rpm back to 500rpm.

[banzai510(hainz)]

As PocketRocket said, I don tthink itsa fuel pump.

But let us know,

 

disconnect the cable if you think its a sticky cable.

 

this is a long shot but make sure the nut on back of the weber is not too tight.

 

as for the fuel pump with different outputs gal wise its still a carb its feeding. But maybe Im missing something.

Let us know.

[racerx]

Okay tried out the L18 fuel pump, that was not the culprit. So I crimp the fuel hose and idled okay idle did not go down like previously but when I got on the road the car dies..so I must have crimp it too much. Will order fuel pump regulator at Winchester, looking into the Holley one. Will aslo check linkages again..did check the nut on back of weber but has a locking type of washer could not check, will check everything prior to buying fuel regulator. Hainz, when you say cable are saying manual choke cable? I have linkages.

[banzai510(hainz)]

I mean the regular throttle cable. Just unwrap it from the pulley then you can tell if it was bindin in the throttle cable houseing. Just isolated it to trouble shoot.Hit the linkage and see if it snaps back. I havnt seen a photo of your setup but the weber has a spring on it, but your truck should also have a RETURN spring also. I light return spring to help the carb spring out. If you dont then get one and adjust everything again and see what happens.

 

As for the Nut in back that bolts the linkage on the butterfly. There is a sloted wssher with a tang to prevent it from backing out. Well anyways I have seen when people tighten the nut they reaaly ref on it and it can bind up. Most will tighten it it will close the butterfly plate but if you over do it it could do soemthing. I seen where idles fine but come off idle it stalls and cuts out. Not that its a proeplm with yours.

 

But I just dont see a need for a regualtor with all these different fuel pumps your using.

[racerx]

Thanks for all of your help..I will check the dist., carb linkage and others that you guys mentioned...fuel regulator will be last.

[spook420]

would this electric fuel pump need a regulator for an L16 with weber carbs? also how close to the tank does it need to be?

 

http://www.summitracing.com/parts/CRT-P4070/

 

i wanted to take the diaphragm fuel pump off the side of the engine so that it wouldnt put any drag on the engine while its running.