Carrera 3.0 Jumping Fuel Pump Relay Question

[Bill Jennings]

I'm about to pressure test my CIS system for the first time due to a couple of symptoms I'm having ie. low idle (950 rpm) at first cold start, difficult hot start and occasional high idle (2000 rpm) when hot.
Is the fuel pump relay on the Carrera 3 the same as shown in my SC Bentley manual?
The relay looks identical but do terminals 30 & 87a do the same thing?
Thanks
Bill

[jason2guy]

i think thatll do it. ur low idle at start is either, low cold control pressure crreating a too rich mixture or the aux air regulator is not opening or a combination or the two.
the high idle when hot is most likely weak advance springs in the distributor advancing the timing and affecting the idle. the hot start issue could be the check valve on the fuel pump. good luck.
BTW- i just found a source for the advance springs. let me know if u need the info. they are nearly impossible to source

[wasserkuhl]

77 Carrera 3.0 doesn't have the Aux air regulator. Well mine doesn't, it has a hand throttle instead.

Bill, does your have a Hand throttle?

[Bill Jennings]

wasserkuhl,
There is a hand throttle handle but I don't think it is connected as moving it has no effect.
I'm hoping to be able to do the pressure tests later today (Sunday) and will post the results.
Cheers
Bill

[boyt911sc]

Bill,

The '76 - '83 CIS wiring diagrams for these models are basically the same for the FP electrical circuit. So, the '77 Carrera 3.0 (special edition) should be the same too. Keep us posted.

Tony

[wasserkuhl]

Originally Posted by Bill Jennings

wasserkuhl,
There is a hand throttle handle but I don't think it is connected as moving it has no effect.
I'm hoping to be able to do the pressure tests later today (Sunday) and will post the results.
Cheers
Bill

Right,

So It may be that either :
a) the handthrottle is no longer connected (and therefore not allowing you to to ease cold starts) or
b) it has had the the later secondary air valve installed (which replaces the need for a Hand Throttle.)

I prefer the hand throttle as I can start the car from cold and set the idle with the throttle and as the car warms to operating temperature I then lower the throttle as it will idle without it being used.

What I would do in your case is see if it has had the later secondary arrangement installed and if not, seek to re connect the hand throttle as this will ease cold starts.

Difficult hot starts , you may find are due to a failed/failing WUR(Warm up regulator) , fuel regulator and /or vacum leaks(less likely).

First place to start is testing both system and control pressures for the right readings, this will then lead you to WUR and then possible vacum leaks.

Vacum leaks can be sourced via spraying carb cleaner on various areas on the CIS system , if the idle rises when you spray it will indicate a leak!

* Careful to not set anything on fire when doing this!!

Of course ensure that the the fuel filter has been replaced recently and that your pump is working correctly as well.

all you will ever need to know can be found at the following link!!

http://jimsbasementworkshop.com/CIS/CIShome.html

[fastfredracing]

The hand throttle has a little plastic thingy that is connected to the handle, it is plastic, and becomes brittle over the years, and breaks. The hand throttle also has very little control over the throttle linkage, and worn bushings in the bellcrank, or at the transmission relay lever will also cause it not to work.

[Bill Jennings]

I finally got around to checking the fuel pressures.
Ambient temp was 65f
Cold engine relay jumped WUR unplugged valve closed 4.8 bar 70 psi
Cold engine relay jumped WUR unplugged valve open 1.1 bar 16psi
Cold engine relay jumped WUR plugged in valve open 2.7 bar 39 psi

Hot engine results

Engine running at operating temp relay in test valve open 3.5 bar 50 psi
Following results all with engine off and test valve open
10 sec 2.2 bar 32 psi
1 min 2 bar 30psi
4 min 1.8 bar 26 psi
8 min 1.7 bar 25 psi
10 min 1.65 bar 24 psi
15 min 1.6 bar 23 psi
20 min 1.5 bar 22 psi
30 min 1.4 bar 20 psi

The symptoms I'm addressing are slow idle (950 rpm) at cold start
Occasional non start when engine very hot.
Occasional idle stuck at (2000 rpm) when engine very hot.
I have the original 5 blade fan and the hot issues occur after being stuck in traffic on a hot day. My oil temp gauge does not work so I am unsure how hot this engine gets.

Cheers

Bill
__________________
1977 Carrera 3.0
This much fun must be illegal!

[wasserkuhl]

Bill,

I strongly recommend getting the Oil temp Gauge working, upgrading to an 11 Blade fan and upgrading the front oil cooler.

Considering the Summer that we are going to get..............STINKING HOT.

[Bill Jennings]

Hi Steve
No argument from me on all three.
I'm trying to source the fan and cooler upgrade at an affordable price.
I am worried that my hot start issue is related to the car running too hot on occasion.
My temp gauge reads at max as soon as you turn the ignition on.
I have checked the wiring and replaced the sender.
I've also tried running a new wire from sender to the gauge.
I'm trying to find an auto electrician that can test the resistance range that the gauge responds to and i have both types of senders and can test their resistance at boiling point then figure out which one to try to recalibrate the gauge to.
At least that is what a instrument shop in Queensland recommends.

I would welcome any other ideas about this as well as a lead on an affordable fan & cooler!

Cheers
Bill