Team Camaro Tech banner

1 - 18 of 18 Posts

·
Registered
Joined
·
513 Posts
Discussion Starter #1
I'll try to keep this brief. During the winter months the I installed the following on my car.

- New Edel. Perf Intake
- New holley mech fuel pump with fuel pressure gauge <--important to problem.
- New Edel. Victor Jr. Water pump
- Spal electric fan with temp. sensor
- Griffin rad.
- new hoses everywhere.
- oil relocation kit with dual filter.

NOW, I started the car for the first time. and got the following results. ALL AT IDLE ON THE DRIVEWAY. 900rpm revving to 3000rpm, timing 10 adv. base timing.

COLD
- Temp 150 deg
- Oil pressure 70lbs (using Mobil 1 trisynth. 10W30
- Fuel press. 7 lbs
- Vac 15

WARM/HOT
- Temp 195deg fan turns on. And turn off at 190deg. Fans turns off too early BUT that's because the sensor is on the intake not on the heads. (I fix soon enough with a manual switch)
- Oil pressure 30 lbs
- Vac. - 15
- Fuel pressure went down to 6, then 5, then 4,3,2 and right down the ZERO?! I tapped the gauge and no response.

PROBLEM 1: Car still idling fine, give it gas, running excellent no problem, but fuel press. gauge still reads 0lbs! No fuel leaks anywhere....seems like the hotter the car got the lower the pressure got.

PROBLEM 2: do these # sound right for hot and cold conditions.

BTW, these are all mechanical gauges, it's a mild 454 and I re-tourqued the intake to 25lbs after the car was hot. :)
Did I miss anything?
Any feedback would be appreciated.
Thanks.

[This message has been edited by mikestr (edited 04-11-2002).]
 

·
Registered
Joined
·
56 Posts
I have a somewhat similar setup as you...454, Edlebrock Performer intake and cam...but with Edlebrock carb and AC Delco fuel pump. I have fuel pressure indication inside the car via an isolater under the hood. I have noticed that my fuel pressure will drift very slowly from 6-7 psig down to 2 or less just cruising down the highway at little or no throttle. I also noticed that if I completely let off the gas the indicated fuel pressure usually quickly recovers. I have never noticed any impact on engine performance. So I quit worrying about it. But I would be interested in hearing if others are having this problem and if anyone has figured out what is going on inside the carb......Scott
 

·
Registered
Joined
·
513 Posts
Discussion Starter #3
<BLOCKQUOTE>quote:</font><HR>Originally posted by ssfrebo:
I have a somewhat similar setup as you...454, Edlebrock Performer intake and cam...but with Edlebrock carb and AC Delco fuel pump. I have fuel pressure indication inside the car via an isolater under the hood. I have noticed that my fuel pressure will drift very slowly from 6-7 psig down to 2 or less just cruising down the highway at little or no throttle. I also noticed that if I completely let off the gas the indicated fuel pressure usually quickly recovers. I have never noticed any impact on engine performance. So I quit worrying about it. But I would be interested in hearing if others are having this problem and if anyone has figured out what is going on inside the carb......Scott<HR></BLOCKQUOTE>

Interesting, but my issue is at idle. Very strange isn't it?! I would ALSO be interested in hearing if others are having this problem.
 

·
Super Moderator
Joined
·
32,447 Posts
Change fuel gauge to a liquid-fill gauge.

Too much vibration for a non-filled gauge.

One can order a stainless steel 0-15 psi, 1 1/2 in dia, bottom fit or back fit, gauge from McMaster-Carr online for $27.

Otherwise, your results look very good, imo.

Usually, sensor is placed in the fins at the return tank(hose to water pump) or, if surface mount, placed on the return tank. You're fighting against block temperature, which will always be higher, typically 20-50 degsF, than coolant temp. I have heard some place the sensor inside upper rad hose.

------------------
Everett 68/350/PG/11.90/115mph
 

·
Registered
Joined
·
513 Posts
Discussion Starter #5
<BLOCKQUOTE>quote:</font><HR>Originally posted by Everett#2390:
Change fuel gauge to a liquid-fill gauge.

Too much vibration for a non-filled gauge.

One can order a stainless steel 0-15 psi, 1 1/2 in dia, bottom fit or back fit, gauge from McMaster-Carr online for $27.

Otherwise, your results look very good, imo.

Usually, sensor is placed in the fins at the return tank(hose to water pump) or, if surface mount, placed on the return tank. You're fighting against block temperature, which will always be higher, typically 20-50 degsF, than coolant temp. I have heard some place the sensor inside upper rad hose.

<HR></BLOCKQUOTE>

Actually it is a liquid filled gauge.
 

·
Registered
Joined
·
2,765 Posts
Is your fuel lines around any hot sources? Could be vapor lock I'm wondering...but wouldn't make too much sense 'cause the car seems to run OK.

------------------
1969 Base Camaro
Vortec 355, Perf. RPM, Demon Carb., TH-400
All sheetmetal is NOS GM
See my NEW webpage at: http://www.geocities.com/compuboy007/
 

·
Super Moderator
Joined
·
32,447 Posts
Either gauge is broke, if equipped, regulator is toast, or fuel pump works as needed or broke.

Everett
 

·
Registered
Joined
·
828 Posts
Mike, does the guage work now? Did it only work once, and now it never moves?

I fought a vapor lock problem on my 69 that I traced to a gas cap that wasn't venting. I installed a friend's fuel pressure guage that had a sending unit so I could see the fuel pressure as I drove around. I have an electric fuel pump, and it would never drop below 5 lbs, and was around 6 1/2 to 7 lbs at idle. That $8 gas cap sure caused a lot of headaches!

------------------
Pics of my 69
 

·
Registered
Joined
·
513 Posts
Discussion Starter #9
<BLOCKQUOTE>quote:</font><HR>Originally posted by Silver69Camaro:
Is your fuel lines around any hot sources? Could be vapor lock I'm wondering...but wouldn't make too much sense 'cause the car seems to run OK.

<HR></BLOCKQUOTE>

No, no hot sources. The car runs fine, I expected it to bog, choke and stall at idle, BUT is rumbles and purrs just fine. That is why this is to strange. Maybe the gauge is bad? BUT I would not expect it to work at ALL, not just when the engine is hot.

Anyone run into this at all?


[This message has been edited by mikestr (edited 04-12-2002).]
 

·
Premium Member
Joined
·
4,817 Posts
By any chance, do you still have the sock inside the tank on the fuel line? Mine quickly got partially clogged from a bad load of gas and I would see a slow pressure drop while driving. I removed it. With a Carter mechanical pump, I see a consistent 6 lbs. When I get on it, it will drop to about 4 but recover quickly.

------------------
Rick Dorion
69 RS Conv,355,M20,4.10's and I don't worry about stone chips ( yet ).
 

·
Registered
Joined
·
513 Posts
Discussion Starter #11
<BLOCKQUOTE>quote:</font><HR>Originally posted by RickD:
By any chance, do you still have the sock inside the tank on the fuel line? Mine quickly got partially clogged from a bad load of gas and I would see a slow pressure drop while driving. I removed it. With a Carter mechanical pump, I see a consistent 6 lbs. When I get on it, it will drop to about 4 but recover quickly.

<HR></BLOCKQUOTE>

If so, would that explain the 7lbs at startup? I would expect it to be 0 from the start.
 

·
Premium Member
Joined
·
4,817 Posts
I'm assuming the crud would 'float away' from the sock when the car was shut off. I'd have good pressure upon starting but lose it as I drove.

------------------
Rick Dorion
69 RS Conv,355,M20,4.10's and I don't worry about stone chips ( yet ).
 

·
Registered
Joined
·
513 Posts
Discussion Starter #13
I wanted to revisit this topic because I still have not solved it. I did some more investigations on when the problem is occuring. It seems that the pressure is fine when car is cold (145-170) as the engine temp. increases, the pressure drops, as I stated before, to zero. I checked the float level, I adjusted air/fuel to the highest manifold vacuum and idle as well. After that, I throttled the engine to 3000rpm and no change.

I'm stumped!
SOS
 

·
Premium Member
Joined
·
4,817 Posts
When you're pressure goes to zero, try disconnecting the line from the output side of the pump. Use a catch can and remote started to check the pump volume. This way you can eliminate causes such as if it is before/after the pump.

------------------
Rick Dorion
69 RS Conv,355,M20,4.10's and I don't worry about stone chips ( yet ).
 

·
Registered
Joined
·
513 Posts
Discussion Starter #15
I installed a clear fuel filter and I get tons of bubbles. Does this mean I have vapour lock? If so, would this cause a hesitation @ high RPMs as well (3500+), along with a low fuel pressure? If so, I do I fix this?

Thanks in advance.




[This message has been edited by mikestr (edited 04-23-2002).]
 

·
Moderator
Joined
·
10,147 Posts
Looks like a plugged fuel tank sock, or a fuel line that is sucking air.
If the pump is sucking too hard against a plugged filter it will either suck air past a fitting or cracked hose, or it will vaporize some fuel due to the extra vaccum in the line.

Try it with your fuel cap removed to see if the cap is not venting correctly.
David

------------------
Check my web page for First Gen Camaro suspension info:
David's Motorsports page
First Gen Suspension Page
67 RS 327 original owner. 69 Camaro Vintage Racer, 65 Lola T-70 Chev SB Can-Am Vintage Racer
 

·
Registered
Joined
·
513 Posts
Discussion Starter #17
<BLOCKQUOTE>quote:</font><HR>Originally posted by davidpozzi:
Looks like a plugged fuel tank sock, or a fuel line that is sucking air.
If the pump is sucking too hard against a plugged filter it will either suck air past a fitting or cracked hose, or it will vaporize some fuel due to the extra vaccum in the line.

Try it with your fuel cap removed to see if the cap is not venting correctly.
David

<HR></BLOCKQUOTE>

I've removed the fuel cap and problem is still occuring. Any other ideas?
 

·
Super Moderator
Joined
·
32,447 Posts
As David P suggested and you also stated in your last post, air bubbles in the filter.

You have a leaky fuel line.

Disconnect the fuel line at both ends, fuel pump and fuel tank, plug one end, the other end, connect to 10 psi of shop air. Pressurize and use soapy solution and spray everywhere on fuel line, steel and rubber. Look for bubbles.

If that proves good,then its either fuel pump fitting or fuel tank sending unit/pick-up. Or maybe fuel pump itself could be leaking internally to the crankcase and sucking a vacuum, or from the atmospheric vent hole.

Everett
 
1 - 18 of 18 Posts
Top