Date: Tue, 27 Aug 2013 21:44:13 -0700
Reply-To: Alistair Bell <albell@SHAW.CA>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Alistair Bell <albell@SHAW.CA>
Subject: Re: Fuel pressure anomaly
In-Reply-To: <BAY179-DS114B037B964EB66BA641A3A04B0@phx.gbl>
Content-Type: text/plain; charset=us-ascii
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
>
