| Author |  Topic  |
EdinburghJoe
V4 Fan
United Kingdom
162 Posts |  Posted - 02 Mar 2020 : 14:20:06  
| Wot no Saab chat? Everyone's cars must be working!
I've had a question that's been mostly at the back of my mind for a while now. During the winter I don't use the 96 much at all, but every couple of weeks I'll take it round the block a few times to keep it moving.
Problem is that it always takes a lot of cranking to get it started. I give it roughly 10 second bursts, with maybe 20 seconds in between bursts. I push the pedal down a couple of times between bursts. There will be nothing at all for maybe the first 2 or 3, then it will catch on maybe the 4th or 5th burst, and be fine thereafter.
I've got a mechanical fuel pump, and I've always understood that the problem is that the fuel in the carb bowl will have evaporated since last use, and I've just got to wait for it to slowly fill and then I'll be in business.
Is there anything I can do to make it start quicker? I don't want to fit an electric fuel pump - the guy who had the car before me had one and I think it got rejected as a 'dangerous modification' at the MOT. I like the safety aspect of a mechanical pump: if the engine stops the fuel stops. Best idea I could come up with was to leave it with the choke on: would the closed choke flap prevent evaporation? This would also hold the throttle open, but I've not done it thinking it could allow corrosion to form around the throttle flap, preventing it closing properly.
It's not a big problem, it's less of a deal when I'm properly using the car, but I wandered if there was any mileage in the choke idea.
Joe |
|
christophe
V4 Fanatic
France
227 Posts | Posted - 02 Mar 2020 : 17:01:59
| Yes, the choke will help to prevent evaporation from the carb but only for a couple of days. Nevertheless, I took the habit of closing it on all my carburetted cars after use as it also prevents moisture to get into the engine. I recently put a new fuel pump on my 96. After cranking for 10 seconds two times and two squirts of the accelerator pedal, the car starts flawlessly even after a few week hiatus. I'd say that your fuel pump might be a little on the weak side. You can check this with a pressure gauge. Of course, the fuel line is also important. Unless your rubber hoses are fairly recent, I would change them as this is cheap insurance. It also helps to keep the fuel tank full. In last resort, a priming bulb would guarantee perfect starting: https://www.amazon.com/Primer-Rubber-Aluminum-Suitable-Motorcycle/dp/B07CYT7MDQ
As far as I'm concerned, a bit of cranking before starting an engine that sat for some time nether bothered me, as I like to get some oil pressure first.
Nice evening to all.
Christophe |  |
|
melle
V4 Guru
United Kingdom
3833 Posts | Posted - 02 Mar 2020 : 17:55:38
| After a few weeks there should still be fuel in the float bowl; just take the top off the carb and have a peek. I doubt closing the choke flap(s) will make any difference to the rate of evaporation or moisture ingress to be honest.
What type of carb do you have? Points or electronic ignition? If it's only the first start after a few weeks I wouldn't worry too much, just squirt some brake cleaner (or a posh equivalent that does exactly the same) down the carb before starting.
quote:
Originally posted by EdinburghJoe
the guy who had the car before me had one and I think it got rejected as a 'dangerous modification' at the MOT. I like the safety aspect of a mechanical pump: if the engine stops the fuel stops.
If that's the case it wasn't installed properly. If you fit an inertia switch the pump will stop in case of a collision/ roll and you can add a fuel pump relay so the pump stops if the engine doesn't turn. I've fitted a Facet pump with both safety features in my 96, probably safer and more reliable than a mechanical pump.
www.saabv4.com | |
|
andydeans3
V4 Guru
United Kingdom
2012 Posts | Posted - 02 Mar 2020 : 19:36:48
| Joe
Fit a check valve (non return valve), between the pump and carb. This stop the fuel draining back, when the car is not being used. It might not be the whole answer, but it will help.
I've actually got a second one fitted under the back seat close to tank as well.
I'm very interested in the comment from the MOT tester. An electric pump is a pretty common modification for these cars, so that surprises me.
Andy
1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro |
Edited by - andydeans3 on 02 Mar 2020 19:39:55 | |
|
melle
V4 Guru
United Kingdom
3833 Posts | Posted - 02 Mar 2020 : 21:27:48
| The original mechanical pump effectively is a check valve, so I don't think there's any merit in fitting another one close to the carb, as there is basically nowhere the tiny bit of fuel in the short line can go. As for fitting one close to the tank, I think the fuel in the long line from the pump to the tank draining back is very much theoretical too. Firstly, for it to drain back it needs air to enter from the carb/ pump side. The only way air could enter, is if the pump doesn't seal properly. If that's the case it won't pump very well either and will need cleaning or a new membrane. Secondly, the majority of the long line is below the fuel level in the tank; the line and tank will act as communicating vessels should any air get in from the pump side for whatever reason (the tank is vented). Even if all fuel would drain back to the tank and the line would be completely empty, a good condition fuel pump should easily suck it full again with only a few cranks of the engine on the starter. Please correct me if I'm missing something in my reasoning!
This may sound controversial, but I think most cold starting issues are electrical faults, i.e. lack of oompf from the ignition, the battery or the starter, or operator error, i.e. not following the correct starting procedure for a specific carb.
www.saabv4.com | |
|
andydeans3
V4 Guru
United Kingdom
2012 Posts | Posted - 02 Mar 2020 : 21:56:45
| Melle
I fitted the check valve up near the carb, when I first bought the car. The car at the time was a bitch to start when it was hot, and fitting the check valve, was a tip given at the time. The problem was in fact the ancient, totally knackered twin choke Solex fitted at the time. When I fitted a new twin choke Weber, the hot start problem was in fact solved.
The reason I fitted the check valve under the seat was at a time, (about 3 years ago) when I had a strange fault that would manifest itself now again, honestly just very occasionally. The car would just stop, open the bonnet, do very little, try the starter, and off she would go.
It was Steve at Malbrad who suggested fitting the check valve under the seat, and the problem totally disappeared.
A check valve in a moving fluid system is always a good idea. (That's the old Oilman talking!)
1978 LHD SAAB 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro | |
|
melle
V4 Guru
United Kingdom
3833 Posts | Posted - 02 Mar 2020 : 23:02:20
| In general, I believe the old oilman is absolutely right. However, in the case of a low pressure fuel system like the V4 has, I'm not convinced fitting one will make a jot of difference. Fuel injection systems, which operate with higher pump pressures, need an accumulator or similar device to retain line pressure.
Years ago when I just had my 96 I was talked into fitting a non-return valve because getting it started was very difficult; it helped because I also adjusted the points and the valves.
www.saabv4.com | |
|
Doive
V4 Fan
United Kingdom
160 Posts | Posted - 03 Mar 2020 : 10:03:48
| When we first bought our V4, it was an absolute pig to start hot, because after investigation it transpired that the ICH float had gone porous, and was allowing fuel to overflow into the inlet manifold & flood the engine. Started like a dream from cold because it was massively overfuelling. Obviously a different issue to the OP. I'd suspect a weak fuel pump taking time to refill the float bowl. Worth doing a flow test on the pump to see how it's running. Ours has an electric pump mounted on the inner wing behind the headlight, which seems to work well despite people suggesting pumps prefer to push than pull.
1970 95 V4 van
1972 Sonett 3
1973 95 V4 estate | |
|
melle
V4 Guru
United Kingdom
3833 Posts | Posted - 03 Mar 2020 : 10:14:18
| quote:
Originally posted by Doive
Ours has an electric pump mounted on the inner wing behind the headlight, which seems to work well despite people suggesting pumps prefer to push than pull.
It entirely depends on the type of pump.
So, you've got a Sonett now? Tell us more! 
www.saabv4.com | |
|
Doive
V4 Fan
United Kingdom
160 Posts | Posted - 03 Mar 2020 : 11:11:32
| quote:
Originally posted by melle
So, you've got a Sonett now? Tell us more!
We have had our Sonett for a few years now, been a great little car & fun during the summer months. Had the floorpans & sills welded up two years ago, and a stainless exhaust custom made to replace the very rotten original. Now needs the water pump replacing, which means the clamshell needs to come off, so been parked in storage since last spring. Still starts without complaint after standing. Great little car, hoping to get if back on the road soon. Have a 34ICH to go on as well, original FOMOCO carb is a bit grumpy at times.
1970 95 V4 van
1972 Sonett 3
1973 95 V4 estate | |
|
GeoffC
V4 Mad
United Kingdom
507 Posts | Posted - 04 Mar 2020 : 09:21:05
| | It is possible to change the water pump on a Sonett III without removing the front end. I did a how to in the Driver magazine some years ago. Pm me and I can send you a link, it was easier than taking the front end off! | |
|
melle
V4 Guru
United Kingdom
3833 Posts | Posted - 04 Mar 2020 : 20:31:42
| Cool collection Doive, I somehow missed you have a Sonett as well.
www.saabv4.com | |
|
Doive
V4 Fan
United Kingdom
160 Posts | Posted - 05 Mar 2020 : 09:42:20
| quote:
Originally posted by GeoffC
It is possible to change the water pump on a Sonett III without removing the front end. I did a how to in the Driver magazine some years ago. Pm me and I can send you a link, it was easier than taking the front end off!
Thanks Geoff, I've read your 'how to' and it's excellent. I think given my recent experience with doing the water pump on the 95, and the appalling access & seized bolts on the rear housing, I fear I may need to take the clamshell off anyway for proper access. I don't work well in confined spaces! Would like to fit an electric cooling fan while I'm in there, and the auxiliary driving lamps, tidy up the wiring, and a dozen other small jobs.
1970 95 V4 van
1972 Sonett 3
1973 95 V4 estate | |
|
GeoffC
V4 Mad
United Kingdom
507 Posts | Posted - 05 Mar 2020 : 20:17:29
| | Ok makes sense to do as many jobs as possible with the front end off. Good luck. | |
|
EdinburghJoe
V4 Fan
United Kingdom
162 Posts | Posted - 09 Mar 2020 : 15:34:59
| Thanks for the replies. I've got a FoMoCo carb with recently fitted accuspark ignition. The ignition timing is OK (I tested it recently with a strobe), the plugs and HT leads are maybe three years old (equating to about 3K miles).
It's not a big deal - if it carries on being difficult to start once I start using the car more in Spring then I'll need to take it more seriously, but for now I was just curious.
One thing that occurs to me after reading the comments above: if the problem was spark rather than fuel then would I be able to smell petrol vapour coming out of the exhaust after cranking the engine (but before it had caught)?
Joe | |
|
melle
V4 Guru
United Kingdom
3833 Posts | Posted - 09 Mar 2020 : 21:58:21
| quote:
Originally posted by EdinburghJoe
One thing that occurs to me after reading the comments above: if the problem was spark rather than fuel then would I be able to smell petrol vapour coming out of the exhaust after cranking the engine (but before it had caught)?
Not necessarily I would think.
Do you follow the correct starting procedure for your carb (press throttle twice before starting)? Have you checked the auto chocke still works? Most FoMoCos I've worked on were pretty clapped out after 40+ years of service.
www.saabv4.com | |
|
| Topic | |
Delayed starting...
