TABBOO

Need some help with fuel pressure problem. I should probably tell the whole story. I was having trouble starting (started fine cold, drove about 10 miles to car show tried to start after sitting 1 hour wouldn't start, let sit some more & it started. Happened several weeks in a row.) I replaced CTS cause some posts say it can make car start hard. No help!!
I thought injectors were leaking by so I pulled all 8 & had cleaned & flow tested.
I didn't have a fuel pressure guage so I didn't do leakdown test.(Have one now.)
I figured orginal in car 19 years needed cleaned anyway.
Got report on injectors bad pattern & varnished but no leakthrough. All injectors good after cleaning. I put car back together with new fuel pressure regulator (adjustable Holley) & I get 28 psi fuel pressure no matter if I adjusted regulaor all the way up. Car won't start, feather pedal when starting & runs but sounds weak, stalls at idle.
I put old fuel pressure regualor in & same story. (28 psi)
I had a new pump in last year (AC-Delco) I can here pump run when I turn key on. My question could I have done something wrong with the regulator or does it sound like a weak pump. I f it is the pump how could it have gone bad in less than 12 months (probably only 800 miles driven). Sorry for long post but wanted to give all info relevent!! Help!! I will be thankful for all opinions!!!

xlwhellraiser

iTrader: (1)

All in all you are getting 28psi fuel preassure. You checked everything else, its pretty sure to say that either its a fuel pump or something is restricting your preassure. I'd check the filter and go from there. Was the pump installed correctly???

TABBOO

I put a new filter on just yesterday after I found low pressure. I thought it was the most logical place to start. Sorry forgot to mention that.
The pump was istalled by a certitied GM mechanic I hope he installed it correctly but if he did I wouldn't think I would be having this problem. The pump has been in almost a year but probably only has about 600 miles on it as I store the car in the winter. I always use stabilizer.
I wonder if there is a way to isolate the pump by the tank to check pressure?

Vader

You can pinch the return fuel line and test pressure again. If the pressure increases with the line pinched, the regulator is suspect.

TABBOO

Vader you are my HERO!!!!!
I pinched the line & got 60 psi. I then unpinch it & recheck & I go back to 28 psi. I have had same problem with both the old & new regulators.
Could I have assembled them wrong? Do you know where I could get a diagram of the regulator. I followed the Holly instructions but maybe an o ring or something in the base of the regulator that I missed that wasn't covered in the directions. I am happy that I don't have to buy a new pump!!!!! Now if I can just get it running by the weekend!!!

xlwhellraiser

iTrader: (1)

Hey thats cool.

I am not sure, but could you possibly install the diaphragm upside down or sumtin. I am having a similar problem right now with my vert. I'd just get a new regulator (just the diaphragm) and than use adjustable housing on it. It should work.
Good luck.


How does your car run???

TABBOO

I think maybe there should be an O ring in the base part of the regulator housing. I see the fuel line tube in the middle is sticking up a little & wonder if there wasn't an O ring that went around it for the spring assembly to seat to. I hope somebody can clarify that for me. I tried the dealer no exploded view of the regulator & parts store same thing Summit same story even Holly. I have new Holly adjustable regulator it seems fine. I can adjust it down to zero when pressurized but can't get over 28 psi. Seems to me there should be something else in there to generate more resistance to flow thereby more pressure since fuel pressure is actually how much resistance to flow you have.

doc

You have the Holley with the large wheel on top? Looking down on the AFPR, you turn the wheel clockwise to increase fuel pressure. You stated that you turned it "up". I'm not sure what you meam. Are you turning the wheel clockwise? That is down and restricts the return line more, for increased fuel pressure.

Vader

Assemble like this:

TABBOO

I think I wasn't clear enough I am sorry. Doc when I said up I meant I turned up the pressure. You are correct that tightening the **** increases pressure.
Vader I also wasn't clear enough I guess in my question. My problem I think is in assembly of the fpr internally & not the fuel rail. I have taken an image from your adjustable fpr pdf & hope it will clarify my question. I am asking if there should be an O ring around the fuel tube in the base of the regulator where the sping assembly is seated.(The spot directly in the center of the regulator base casting) I am sorry for not being clear enough.
I tried to zoom in on the regulator base casting but due to resolution I couldn't quite tell if there is an O ring or something in the seat of the base casting.
I tried just to lift the image of the base casting of the regulator but I am not good enough with pdf to do that.Sorry!!!

TABBOO

Just a continuation. I did some more testing with the fuel pressure guage.
If I test the whole circuit I get 28 psi & then it leaks down to about 10 psi in about 10 minutes.
If I block the return line I get 70 psi & in 15 minutes it leaks down to 62 psi.( I will assume this is just the fuel line I crimped with vise grips leaking by)
So I must think I have no leaks visible or not in the fuel rail assembly.
If I unblock the return line at 70 psi it drops immediately to about 25 psi.
I wonder could this be the check valve at the pump?
I am totally confused & ready to blow this damn thing up!!!
HELP!!!!

doc

Well, I am not an expect, but I would tend to suspect the AFPR unit. I would bleed off all fuel pressure and remove the AFPR & inspect it.

Vader

Since you have already blocked the return line, and pressure remains at 62 PSIG after 15 minutes, that proves the check valve in the pump is not leaking down enough to cause a problem - That is what that procedure tests.

Since pressure drops to 25 PSIG once the regulator return is opened, I'd suspect you have an incorrectly calibrated spring in the pressure regulator. The pressure should fall off to no less than about 42 PSIG, since there is no pilot vacuum to compress the spring. Your FPR needs a new spring.

TABBOO

I now have plenty of fuel pressure.
The whole problem was the Holly AFPR. The Holly AFPR is a beautiful looking expensive piece, you think you are buying the best BUT... it must be machined in China!!! I looked at 3 seperate Holley AFPR s at Summit some still had metal shavings from machining on them in the sealed bags. The adjustment screw is a **** on the top, I saw all three screws machined into the ***** on the 3 AFPRs looked like they were different lenghts. I traded for a BBK & I now have 46 psi set into it to try to see if that improves performance. I hope this is a good starting point for a 305 TPI. I saw the post in FAQ & it said 46 psi was a good set point, I hope there won't be much difference between my 305 & the 350 in the post as far as benefits from using the 46 psi setting go.
I tried to start it & now have no spark!!!! I suspect the Accel 4 pin pickup I put in the distributor is probably shot. I have heard they don't last. I will put the AC Delco one that was in the car back & hope for the best!!!!