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Question: fuel pressure regulator ??

hotrod2

Well-known member
Joined
Jul 11, 2014
Messages
50
Location
illinois
Corvette
1985 c4
hi everyone ,my question is ,,, 20 psi of pressure at regulator not 40 , runs but doesn't rev,prolly cause its starving,has a bad regulator caused this b4? also the fan relay is gone ,the fan is hotwired to a toggle ,but the other 2 wires to the relay are going to nothing ,, i will fix this horrible wiring eventually , the fan relay goes to the computer ,fuel pump has 12v at the wires from the pump relay i think the relays are inner connected and will keep the timing from advancing do you think this is electrical or mechanical problem from the regulator is a aftermarket pressure regulator diaphragm a good deal,i,think it would be a good thing to replace for a starting point p.s...... car will stay running with the pressure regulator un hooked,! seems odd to me new to these regulator issues,thanks for any advice
 
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ecss

Well-known member
Joined
Nov 27, 2004
Messages
649
Location
Windsor Mill, MD
Corvette
89 Brilliant Red Metallic
hi everyone ,my question is ,,, 20 psi of pressure at regulator not 40 , runs but doesn't rev,prolly cause its starving,has a bad regulator caused this b4?

The only thing inside the fuel pressure regulator is a spring and diaphragm.
If the diaphragm is leaking, you will see fuel in the vacuum hose.
I doubt the spring is bad, most likely the fuel pump is bad, the fuel filter on the passenger side frame rail or fuel pump filter sock is clogged or you have a leaking injector. You can carefully pinch off the fuel rail return line rubber hose at the fuel pump sender assembly and see if the fuel pressure rises. You need to remove the gas tank lid and rubber boot to see it.

If you turn the ignition off, how fast does the fuel pressure drop? The pressure should hold for at least 10 minutes and slowly bleed off.


also the fan relay is gone ,the fan is hotwired to a toggle ,but the other 2 wires to the relay are going to nothing ,, i will fix this horrible wiring eventually , the fan relay goes to the computer ,fuel pump has 12v at the wires from the pump relay i think the relays are inner connected and will keep the timing from advancing do you think this is electrical or mechanical problem from the regulator is a aftermarket pressure regulator diaphragm a good deal,i,think it would be a good thing to replace for a starting point p.s...... car will stay running with the pressure regulator un hooked,! seems odd to me new to these regulator issues,thanks for any advice

There is no connection with the fan relay or fuel pump relay with ignition timing.

Here's a schematic of the fan circuit.

 
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Hib Halverson

Technical Writer for Internet & Print Media
Joined
Jan 10, 2001
Messages
13,453
Location
CenCoast CA
Corvette
71 04 12 19
dude
u prolly need to, like... diagnose the fuel system totally per the fsm
same w the fans.
w your car, the pri fan is cont by the outer but the sec fan is run by a fan sw in the right head
 

hotrod2

Well-known member
Joined
Jul 11, 2014
Messages
50
Location
illinois
Corvette
1985 c4
The only thing inside the fuel pressure regulator is a spring and diaphragm.
If the diaphragm is leaking, you will see fuel in the vacuum hose.
I doubt the spring is bad, most likely the fuel pump is bad, the fuel filter on the passenger side frame rail or fuel pump filter sock is clogged or you have a leaking injector. You can carefully pinch off the fuel rail return line rubber hose at the fuel pump sender assembly and see if the fuel pressure rises. You need to remove the gas tank lid and rubber boot to see it.

If you turn the ignition off, how fast does the fuel pressure drop? The pressure should hold for at least 10 minutes and slowly bleed off.




There is no connection with the fan relay or fuel pump relay with ignition timing.

Here's a schematic of the fan circuit.


i have a book an read the fan relay is tied in with oil temp and timing some how i will read up again/ i only have 1 fan/i had the pump out and it looked good /strainer ect....
i have a near new gas tank/and a new ac delco pump kit /need a new sending unit money is tight and am doing a few other important things
it loses the fuel pressure almost instantly it has 20psi and drops to 10 when started and running
it wouldnt rev at all until i found a melted wire on the maf connector! "that goes to the f pump" fixed it and the small red positive wire from the starter and its a lot better now /dumb bitch at oreilly auto put .045 on my new plugs for the gap and now i read the book says .035! so that needs done and it was a pain to put a few in she cost me time and pain :( sory for cuss word if its not allowed
and the vac lines are crappy

thanks for the replys
 

ecss

Well-known member
Joined
Nov 27, 2004
Messages
649
Location
Windsor Mill, MD
Corvette
89 Brilliant Red Metallic
Has the car ever run properly since you've owned it?

Fuel pressure should be close to 40 psi so you need to fix that problem.

You said you have a new Delco pump installed. What was the original pumps pressure?

Do both pumps have the same symptom?

Pinch off the fuel return line and see what the pressure is.

On the fuel sending unit where the fuel pump mounts to, there was a pulsator that some people remove and replace with a short length of rubber fuel hose. If they didn't use the proper type of fuel hose it could be leaking or the clamps could be loose.
 

hotrod2

Well-known member
Joined
Jul 11, 2014
Messages
50
Location
illinois
Corvette
1985 c4
Has the car ever run properly since you've owned it?

Fuel pressure should be close to 40 psi so you need to fix that problem.

You said you have a new Delco pump installed. What was the original pumps pressure?

Do both pumps have the same symptom?

Pinch off the fuel return line and see what the pressure is.

On the fuel sending unit where the fuel pump mounts to, there was a pulsator that some people remove and replace with a short length of rubber fuel hose. If they didn't use the proper type of fuel hose it could be leaking or the clamps could be loose.



i don have the new pump in yet im waitin to get the new sending unit and ill put the new tank and all in
i bought the car not running but got it going lil by lil
i dont know much about pres regulators lol i know they regulate f pressure lol but my car runs the same with it hooked up or not! lol this makes me think its a problem
i might put small video clip on i know good ppl like to help and is fun figuring it out /so i want to make sure to give the solutions as i go /she is a hoopty but it will be nice when its done
 

Hot Rod Roy

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Joined
Jul 6, 2005
Messages
317
Location
Mission Viejo CA
Corvette
Yellow '84 Coupe
I have a book and read the fan relay is tied in with oil temp and timing some how. Dumb bitch at O'Reilly Auto put .045 on my new plugs for the gap and now i read the book says .035! So that needs done and it was a pain to put a few in. She cost me time and pain. The vac lines are crappy.

You need to trash that book if that's what it says about your fan relay! Is that the same book that says .035 for your plugs? Do you have an Owners Manual for your '85? My '84 OM says .045 gap, and I suspect the very talented woman with the computer at O'Reilly's got it right, so you probably owe her an apology! If your vac lines are bad, nothing will work right! Fix them first!

I don't know much about pres regulators lol. My car runs the same with it hooked up or not! lol This makes me think its a problem.

Bad logic here. If your fuel pressure is low and the fuel pressure regulator is good, the car will run the same whether the regulator is hooked up or not. The regulator only keeps the pressure from going too high! You really do need a Factory Shop Manual (FSM) to do the job right. ( I had fun fixing your text so I could figure out what you were saying.)

:w
 
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hotrod2

Well-known member
Joined
Jul 11, 2014
Messages
50
Location
illinois
Corvette
1985 c4
fuel woes

sorry guys i havent been here in a while, no my manual is correct the 84 plug gap is different than the 85

it needed a new tank , so i got a new tank, fuel sending unit, and new acdelco pump, new regulator, so i got it running and, it was the regulator, now the damn thing isnt holding pressure in the rail like its suppose to
the new regulator had machine marks in it -new, so i now thats why it wouldnt hold pressure but would build pressure when key was on
im trying to get it to hold pressure , the injectors nor seals are leaking "thank GOD" as i did the pinch test like the manual says and it held at 90psi, it had a bad wire to the maf sensor,-fixed it bad wire to the starter /red wire -wouldnt charge or light up dash, i have a new fan relay pig tail, not in yet
it was running great ,working on exhaust and pressure issues now
still need to track down the no power at window switches issue, "new switches",relay is good,getting power to the motors, motors work cause i jumped them and they work fine

sorry for delayed response ill get there some how hopefully soon:thumb lol
 

ecss

Well-known member
Joined
Nov 27, 2004
Messages
649
Location
Windsor Mill, MD
Corvette
89 Brilliant Red Metallic
still need to track down the no power at window switches issue, "new switches",relay is good,getting power to the motors, motors work cause i jumped them and they work fine

The power window circuit doesn't use a relay. Power comes from the PWRWDO circuit breaker. There should be 12 volts on the Pink wire at each switch when the ignition is On.

 

hotrod2

Well-known member
Joined
Jul 11, 2014
Messages
50
Location
illinois
Corvette
1985 c4
thank you,

The power window circuit doesn't use a relay. Power comes from the PWRWDO circuit breaker. There should be 12 volts on the Pink wire at each switch when the ignition is On.







thank you i dont know whats wrong i do have power to a wire as i did jump them both windows and they went up and down, i bought 2 new switches and still nothing from them lol ill look into it as i still need to put in a regulator strip so panel is still off, where is the breaker located?
 

ecss

Well-known member
Joined
Nov 27, 2004
Messages
649
Location
Windsor Mill, MD
Corvette
89 Brilliant Red Metallic
thank you i dont know whats wrong i do have power to a wire as i did jump them both windows and they went up and down, i bought 2 new switches and still nothing from them lol ill look into it as i still need to put in a regulator strip so panel is still off, where is the breaker located?

The power window circuit breaker is located in the passenger side end of dash fuse panel.

 

hotrod2

Well-known member
Joined
Jul 11, 2014
Messages
50
Location
illinois
Corvette
1985 c4
thank you i dont know whats wrong i do have power to a wire as i did jump them both windows and they went up and down, i bought 2 new switches and still nothing from them lol ill look into it as i still need to put in a regulator strip so panel is still off, where is the breaker located?

The power window circuit breaker is located in the passenger side end of dash fuse panel.


yes i checked those i forgot its been a while ,money its tight so this is a long term fixer upper lol but thats why i dont understand why no power to switches, you know,- i have power from those , and window up and down by jumping wires but not through the switches :hb
 

ecss

Well-known member
Joined
Nov 27, 2004
Messages
649
Location
Windsor Mill, MD
Corvette
89 Brilliant Red Metallic
yes i checked those i forgot its been a while ,money its tight so this is a long term fixer upper lol but thats why i dont understand why no power to switches, you know,- i have power from those , and window up and down by jumping wires but not through the switches :hb

Does your cigar lighter work?
Does the center console bulb light when you open the console lid?

Both use the same ground wire as the power window motors.
 

hotrod2

Well-known member
Joined
Jul 11, 2014
Messages
50
Location
illinois
Corvette
1985 c4
Does your cigar lighter work?
Does the center console bulb light when you open the console lid?

Both use the same ground wire as the power window motors.

youll have to forgive me mine is a junker those things are gone or broke lol, my console lid is gone ., but doors light up when opened dunno about lighter i dont smoke so i never tried , ill have to get one and try it the hatch pops from the center console switch though
 

DonB

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Mar 25, 2015
Messages
339
Location
Chicago
Corvette
2019 ZO6 in Elkhart Lake Blue
All I can add here hotrod2 is to fix all your vacuum leak issues FIRST. The engine won't run worth a $hit if it is sucking air everywhere. It should pull a minimum of 18" of manifold vacuum at idle. Also, the plug gap is specific to the type of spark plug and head used, be it cast iron or aluminum. Look your plugs up on Rock Auto and they will tell you the correct gap.

I'm sure the girl at O'Riely's did you good. I have a good one by me and if she gave you the wrong plug and gap, you probably gave her the wrong info! If it's a Cast iron head, I'd guess you probably have an R45TS or a FR5LS plug, which gap at .035. For the .045 gap it is probably an AC/Delco#1 for iron heads(and a A/C #5 for aluminum, which is what I have.) I don't deal with other brand plugs.
No need to get all worked up about the physics of it, unless you are racing. Which you are not. The correct gap for the plug and the right mixture, "in-time" will make it "POP" just fine. You'd be surprised how little it takes to ignite a well compressed correct mixture of fuel and air.

GET A FSM ! They sell them at Corvette Central on disk. Make sure to get the RED COVER manual with the electrical supplement. You being in Illinois, get to know Corvette Central, they are in Sawyer, Michigan and MAMotorworks. They are in Effingham, IL. Both are good people to deal with and ship Fassssssst! They also have good technical departments.

As far as electrical, I'd start with the grounds. There are large grounding points on the lower side where the engine meets the bell housing. Clean them up! Those cause a lot of issues. Also being an older Vette and as you said a "junker;" I'm sure some earlier "electrical wizards" have had their way with it. Be aware of that and try to inspect and correct what you can with the FSM.

Good Luck.

Don.
 
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hotrod2

Well-known member
Joined
Jul 11, 2014
Messages
50
Location
illinois
Corvette
1985 c4
All I can add here hotrod2 is to fix all your vacuum leak issues FIRST. The engine won't run worth a $hit if it is sucking air everywhere. It should pull a minimum of 18" of manifold vacuum at idle. Also, the plug gap is specific to the type of spark plug and head used, be it cast iron or aluminum. Look your plugs up on Rock Auto and they will tell you the correct gap.

I'm sure the girl at O'Riely's did you good. I have a good one by me and if she gave you the wrong plug and gap, you probably gave her the wrong info! If it's a Cast iron head, I'd guess you probably have an R45TS or a FR5LS plug, which gap at .035. For the .045 gap it is probably an AC/Delco#1 for iron heads(and a A/C #5 for aluminum, which is what I have.) I don't deal with other brand plugs.
No need to get all worked up about the physics of it, unless you are racing. Which you are not. The correct gap for the plug and the right mixture, "in-time" will make it "POP" just fine. You'd be surprised how little it takes to ignite a well compressed correct mixture of fuel and air.

GET A FSM ! They sell them at Corvette Central on disk. Make sure to get the RED COVER manual with the electrical supplement. You being in Illinois, get to know Corvette Central, they are in Sawyer, Michigan and MAMotorworks. They are in Effingham, IL. Both are good people to deal with and ship Fassssssst! They also have good technical departments.

As far as electrical, I'd start with the grounds. There are large grounding points on the lower side where the engine meets the bell housing. Clean them up! Those cause a lot of issues. Also being an older Vette and as you said a "junker;" I'm sure some earlier "electrical wizards" have had their way with it. Be aware of that and try to inspect and correct what you can with the FSM.

Good Luck.

Don.

hi thanks for the help, i like to talk to ppl on here more than anything
i have a haynes manual it is really good, this is why i know she told me the wrong gap, she is a ... well something else she has told me wrong on numerous occasions i dont know why without knowing her you would insist she was right but she isnt and i had to do more work because of it
its just a old car with a few bugs it was well used so it should be a good car again, after things are fixed
corvette central are great ppl ,thanks
my big problem at the moment is getting a regulator diaphragm to seal and hold pressure in the rail instead of sending it to the gas tank someone wired the fan relay to a toggle i have a new pig tail for it and fixed a couple other wires
electrical- issues some kids had it and jumped the battery trying to start it and burnt a couple wires i fixed those it runs great but the diaphragm is a pain in the .....
headlight chirps , just the left one, im guessing its the bushings cause others have had issues with them
parts are pricey on a low budget so it is going slowly but i have mad a lot of progress
thanks again to everyone
 

DonB

Well-known member
Joined
Mar 25, 2015
Messages
339
Location
Chicago
Corvette
2019 ZO6 in Elkhart Lake Blue
hi thanks for the help, i like to talk to ppl on here more than anything
i have a haynes manual it is really good, this is why i know she told me the wrong gap, she is a ... well something else she has told me wrong on numerous occasions i dont know why without knowing her you would insist she was right but she isnt and i had to do more work because of it
its just a old car with a few bugs it was well used so it should be a good car again, after things are fixed
corvette central are great ppl ,thanks
my big problem at the moment is getting a regulator diaphragm to seal and hold pressure in the rail instead of sending it to the gas tank someone wired the fan relay to a toggle i have a new pig tail for it and fixed a couple other wires
electrical- issues some kids had it and jumped the battery trying to start it and burnt a couple wires i fixed those it runs great but the diaphragm is a pain in the .....
headlight chirps , just the left one, im guessing its the bushings cause others have had issues with them
parts are pricey on a low budget so it is going slowly but i have mad a lot of progress
thanks again to everyone

I didn't mean to defend the girl at your local O'Riely's. She does sound snooty! I was just saying the girl at my local O'R's is pretty good and easy on the eyes too. It is usually as plain as day on their computer. I've used the computer at my local place to help her locate stuff for me. Parts for these old Vettes are getting harder all the time to get.

But, yes the regulator is a P.I.T.A. to replace. Do NOT attempt to pull the cover back down into place with the screws. Use a "C" clamp or a vise to squeeze it back together to overpower the spring.. Otherwise you can and will rupture the new diaphram and be right where you started without ever knowing you messed up.! Once again, I wouldn't use anything here but A/C-Delco. Mine has the tamper-proof torx screws so you may need a special torx for it. I got one at Home Depot. I believe it was a #10 or #15. I bought the whole set.

Good Luck.
 

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