Date: Wed, 28 Aug 2013 00:52:25 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: Fuel pressure anomaly
In-Reply-To: <ED064E1B-FD7C-4162-8572-F17206CA1D17@shaw.ca>
Content-Type: text/plain; charset="US-ASCII"
Get a long hose for the fuel pressure gauge so you can read it while
driving. If the pressure is good while the bucking is present that is not
the problem. Pumps can be intermittent and affected by temperature.
Dennis
-----Original Message-----
From: Alistair Bell [mailto:albell@shaw.ca]
Sent: Wednesday, August 28, 2013 12:44 AM
To: Dennis Haynes
Cc: <vanagon@GERRY.VANAGON.COM>
Subject: Re: Fuel pressure anomaly
All those issues were dealt with. O2 sensor, temp in sensor etc all checked,
grounds, connections, resistances.
I think I mentioned that a while back when I first posted about this
bucking issue. You might recall that this issue only occurred 3 time
previously, about 18 months apart, only in summer, and 3 of the 4 times was
on logging roads.
The issue I was trying to get across was that I now have the bucking
happening, not as severe as it sometimes is, on regular streets AFTER I
swapped in a different fuel pump. And that I noticed the fuel pressure not
holding when tested tonight.
Alistair
On 2013-08-27, at 9:12 PM, Dennis Haynes <d23haynes57@hotmail.com> wrote:
> Getting bad gas is very rare with todays tanks and fuel distribution
> network. The Syncro having a high mounted plastic tank makes it rare
> to have a fuel storage problem on the vehicle itself.
> The short pump inlet and overall design of the fuel delivery system
> also makes issues like vapor lock and other weirdness's rare also. The
> ability of the system to hold pressure after shut down is not much of
> an issue like it was on the CIS systems. If the pump has enough
> capacity to make pressure and the regulator is working all is good. Leaky
injectors are easy to check.
> Remove them, jump the pump and look for leaks. Then get them to spray
> and check the spray patterns. A bad injector will be obvious.
>
> Intermittent bucking and poor running can indicate an over rich
> condition which is most likely being brought on by an O2 sensor
> problem. Easy test is to cycle the ignition while the problem is
> happening. If the problem immediately clears up for short while you
> have an O2 sensor or wiring problem. Besides the sensor and wiring to
> it a common problem is a bad ground. On the early Syncros the ground
> wire for the distributor harness was usually connected at the base of
> the oil breather tower. This connection is also the ground reference
> for the O2 sensor. The plastic tower makes for a lousy connection.
> Relocate this ground and also check the connection to that ring terminal.
>
> If the O2 sensor test does not indicate a problem there than the next
> thing to check is the temp sensor. These sensors themselves rarely go
> bad but the connector and wiring is often a problem. So is the ground in
the harness.
> Get your ohm meter and check the ground connection (brown wire) from
> the sensor to the chassis. If you can measure any significant
> resistance add another ground to this wire. It is common to see 10-20
> ohms here. Should be almost "0".
>
> Dennis
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On
> Behalf Of Alistair Bell
> Sent: Tuesday, August 27, 2013 11:24 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Fuel pressure anomaly
>
> I have posted about my intermittent bucking and poor running with my
> 86 syncro, something that occurred only sporadically, in summer, and
> all but one time on rough logging roads. Until the last time I was
> putting it down to bad gas.
>
> Last weekend I had the chance to swap in a used fuel pump. I drained
> the tank while doing this and did not find any crud or water. After
> the swap the van exhibited the bucking and missing behaviour. I
> checked other things, arm track, connections etc etc.
>
> I had checked the swapped pump delivery rate out of the van and it
> seemed ok, but tonight I decided to check it again by the book.
>
> I got 600 ml in 30 seconds, Bentley says min rate of 500 ml in 30 sec.
>
> Then I checked pressure, all to spec. So I turned off engine and went
> back... Saw the pressure gauge dropping fast. That's not right, it
> should hold pressure. I started engine again and turned it off, pressure
held.
>
> Started again and off again, pressure dropped. I tried clamping off
> return line and it did slow the rate of press loss.
>
> Then I started van again, no clamps, pressure held. Held to spec. Only
> dropped 2 psi ( 33-30) in 10 min.
>
> The pressure drop occurrence could not be replicated consistently. I
> do suspect the fuel press reg but I need to rule out a leaky injector
> ( mind you, no gas smell from exhaust on restart).
>
> Dennis, what do you think?
>
> Alistair
>
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