[DeTomaso] Pantera low fuel pressure indication
audionut at hushmail.com
audionut at hushmail.com
Fri May 18 17:39:26 EDT 2018
Hey Mike--
Pull the pump, take it apart and have a look?
Just dealt with a similar problem on my old Cadillac (1960 390
V8/modern Edelbrock Performer 4 barrel). The car was consuming fuel
pumps at the rate of 1 - 2 per year. Disassembly of the failed pumps
always showed the same thing: press-fit valve popped loose from it's
bore indicating that it was being overworked.
I started at the tank by pulling a hose end off the tank spigot and
it flowed prodigiously. I then checked the fuel lines for kinks
forward from there. All these looked fine. Fuel filter was okay, no
restrictions in the carb inlet.
This may bear no relation to your situation, but the problem turned
out be chronic back pressure created by intermittent vapor lock.
Apparently modern 91 boils at a lower temperature than it used to.
Removing the carb also revealed an open conduit from the exhaust
through the intake manifold venting directly on the carb base/throttle
plate. This bit of brilliant caveman design was a solution way back
when to enable an engine to warm up quicker. I blocked the open
conduit with a metal gasket that had no opening for that and also used
a heat-shielding thick paper gasket on top of that.
In the spirit of overkill, which always seems like a good idea on old
cars, I also installed a modern cold air intake to further keep the
carb cool. Recently did 6 hours to Vegas and back and no problems.
In your scenario the only thing that comes to mind is that using 2
filters may be overworking the fuel pump? These modern replacement
pumps (or so I've heard) can be of poor quality due to parts companies
assigning manufacturing to the lowest bidder and more often than not,
China gets the contract. Perhaps your fuel pump is doing it's best
with a slightly dislodged valve inside?
John #5909(See you in Monterey!)
Sent using Hushmail
On 5/18/2018 at 12:55 PM, "Julian Kift" wrote:Assuming it isn't the
pump (but really sounds like it is) it can only really be a
restriction on the pump feed side; sock on fuel pickup or one of your
filters blinded?
You say a new tank, is this a 'new to you' tank perhaps even
refurbished or brand spanking new? The former could perhaps have a
coating that has failed and come off?
Julian
________________________________
From: DeTomaso on behalf of Mike Drew via DeTomaso
Sent: Friday, May 18, 2018 12:32 PM
To: De Tomaso Forum
Subject: [DeTomaso] Pantera low fuel pressure indication
Hi guys,
Getting my Pantera ready for Monterey. It received a new fuel tank a
couple of. Moths ago and was started for the first time and all seemed
well. After sitting for a month it was very hard to start, requiring
multiple manual injections of gas into the carb. Eventually it
started and continued to run, and revs happily in neutral to 5000 rpm.
But at idle it registers somewhere between 0 and 1/2 psi of fuel
pressure. At 3000 rpm it goes to about 2 psi.
Besides the obvious (bad fuel pump) what could cause such a thing?
There are no indications of a leak anywhere. The tank has five gallons
of gas. I have two fuel filters, one of them mondo sized.
See video here:
https://youtu.be/jqNnqP_kxH4
Thoughts?
Mike
Sent from my iPad
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-------------- next part --------------
Hey Mike--
Pull the pump, take it apart and have a look?
Just dealt with a similar problem on my old Cadillac (1960 390
V8/modern Edelbrock Performer 4 barrel). The car was consuming fuel
pumps at the rate of 1 - 2 per year. Disassembly of the failed pumps
always showed the same thing: press-fit valve popped loose from it's
bore indicating that it was being overworked.
I started at the tank by pulling a hose end off the tank spigot and it
flowed prodigiously. I then checked the fuel lines for kinks forward
from there. All these looked fine. Fuel filter was okay, no
restrictions in the carb inlet.
This may bear no relation to your situation, but the problem turned out
be chronic back pressure created by intermittent vapor lock.
Apparently modern 91 boils at a lower temperature than it used to.
Removing the carb also revealed an open conduit from the exhaust
through the intake manifold venting directly on the carb base/throttle
plate. This bit of brilliant caveman design was a solution way back
when to enable an engine to warm up quicker. I blocked the open
conduit with a metal gasket that had no opening for that and also used
a heat-shielding thick paper gasket on top of that.
In the spirit of overkill, which always seems like a good idea on old
cars, I also installed a modern cold air intake to further keep the
carb cool. Recently did 6 hours to Vegas and back and no problems.
In your scenario the only thing that comes to mind is that using 2
filters may be overworking the fuel pump? These modern replacement
pumps (or so I've heard) can be of poor quality due to parts companies
assigning manufacturing to the lowest bidder and more often than not,
China gets the contract.
Perhaps your fuel pump is doing it's best with a slightly dislodged
valve inside?
John #5909
(See you in Monterey!)
Sent using Hushmail
On 5/18/2018 at 12:55 PM, "Julian Kift" <julian_kift at hotmail.com>
wrote:
Assuming it isn't the pump (but really sounds like it is) it can
only really be a restriction on the pump feed side; sock on fuel
pickup or one of your filters blinded?
You say a new tank, is this a 'new to you' tank perhaps even
refurbished or brand spanking new? The former could perhaps have a
coating that has failed and come off?
Julian
________________________________
From: DeTomaso <detomaso-bounces at server.detomasolist.com> on behalf
of Mike Drew via DeTomaso <detomaso at server.detomasolist.com>
Sent: Friday, May 18, 2018 12:32 PM
To: De Tomaso Forum
Subject: [DeTomaso] Pantera low fuel pressure indication
Hi guys,
Getting my Pantera ready for Monterey. It received a new fuel tank a
couple of. Moths ago and was started for the first time and all
seemed well. After sitting for a month it was very hard to start,
requiring multiple manual injections of gas into the carb.
Eventually it started and continued to run, and revs happily in
neutral to 5000 rpm.
But at idle it registers somewhere between 0 and 1/2 psi of fuel
pressure. At 3000 rpm it goes to about 2 psi.
Besides the obvious (bad fuel pump) what could cause such a thing?
There are no indications of a leak anywhere. The tank has five
gallons of gas. I have two fuel filters, one of them mondo sized.
See video here:
[1]https://youtu.be/jqNnqP_kxH4
Thoughts?
Mike
Sent from my iPad
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