| Author |  Topic  | |
christophe
V4 Fanatic
France
227 Posts |  Posted - 23 May 2022 : 09:06:59  
| Hello folks,
Some time ago, I noticed my car slightly starved for fuel while on the highway. My engine is a 1.7l coming from a Transit. I do not know if the current carb is original to the car. Some data says it came from a 1,1l Fiesta! It got a 132 main jet, a little bit on the lean side to me. I thought I had found spare jets on ebay but these came with the wrong thread (5/16" instead of 1/4"). So, I'll gladly buy one if somebody was willing to sell.
Nice day to all. |
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melle
V4 Guru
United Kingdom
3833 Posts | Posted - 23 May 2022 : 09:40:24
| What symptoms made you think it was a fuel starvation problem? The 132 main jet should be fine I suppose (std for a 1.5 is 130). If the engine is supposedly running lean and fuel provision to the carb is OK, I would rather suspect an air leak, a clogged emulsion tube (which cannot be removed/ replaced), or an ignition issue.
www.saabv4.com |  |
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christophe
V4 Fanatic
France
227 Posts | Posted - 23 May 2022 : 13:56:25
| Hello Melle,
Glad to hear to hear from you. When this occured the last time, I simply pulled the choke a little and the default desappeard. So, I know this is not an ignition problem. There are no air leaks as well. As for the clogged emulsion tube, I can treat the carb to an ultrasonic bath; but is there a way to assess its condition before dismantling everything? | |
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melle
V4 Guru
United Kingdom
3833 Posts | Posted - 23 May 2022 : 14:28:02
| When does the problem occur, on acceleration or during cruising?
www.saabv4.com | |
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christophe
V4 Fanatic
France
227 Posts | Posted - 23 May 2022 : 15:09:14
| | Only when cruising under 80-90 kmh, which is rather annoying as these are the current speed limits. I do not seem to feel it when cruising at 110 kmh, but my ears don't tolerate this for long! | |
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melle
V4 Guru
United Kingdom
3833 Posts | Posted - 23 May 2022 : 17:38:08
| Since you haven't mentioned idling issues, this sounds like an ignition problem to me. If there is no decent spark at high rpm/ low load, the mixture leaves largely unburnt via the exhaust, which results in a stutter/ the engine holding back. This can to an extent be "fixed" by applying a little choke.
I would start by checking all the ignition wiring and the points gap and condition. It's also worth checking what's left of the fibre/ bakelite/ plastic heel that runs on the distributor shaft; if worn away the points won't open properly, which affects dwell time, which in return results in low output from the coil and the coil heating up. You can check if the coil gets very hot after a motorway run. It may also be worth checking spark at idle, if it's red/ weak it is likely the condenser is on the way out.
Unfortunately this is one of those issues that can have multiple causes, but ignition is worth checking anyway before "fixing" things by starting to replace parts I suppose.
PS: a set of decent (motorbike/ convertible) earplugs is a good idea anyway, I always use them in a V4 on the motorway, mainly because of the wind noise.
www.saabv4.com | |
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christophe
V4 Fanatic
France
227 Posts | Posted - 23 May 2022 : 18:14:34
| | All the ignition components are in top notch condition. They've been replaced not so long ago. Settings are just on the spot. I ran into the very same trouble on my Simca 9 a few years ago when they started to put ethanol in gasoline. A slightly larger main jet solved it. Solex carbs were designed for a 0,731 gasoline density. I suspect this is not the case anymore. | |
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melle
V4 Guru
United Kingdom
3833 Posts | Posted - 23 May 2022 : 19:38:43
| I was assuming this was a new issue that suddenly appeared, which I thought would rule out the scenario you describe. Or has the fuel in France changed again recently? Re new ignition parts: new does not necessarily equal good unfortunately, there's a lot of crap on the market, especially when it comes to condensers.
I have a 130 main that that you could ream to size if that helps? I may have bigger ones in my workshop if you're not in a rush, I'll be there end of June/ early July I think. is your engine a low or high compression 1.7?
www.saabv4.com | |
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christophe
V4 Fanatic
France
227 Posts | Posted - 24 May 2022 : 08:22:26
| | I've been dealing with that annoyance since I have the car. Sometimes, it is less apparent but still there. A 130 jet would do fine. I would ream it at 135 and start from there. I prefer to have an extra jet to do this and keep what seems to be the original one intact. My engine is an MXB (1,7l LC). There is no rush at all, of course. If you need the two extra jets (140 & 145) I ordered, they are yours. | |
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melle
V4 Guru
United Kingdom
3833 Posts | Posted - 24 May 2022 : 09:17:44
| Ah, sorry for misunderstanding that this was a new phenomenon, now it makes more sense that what you described may be fuel related. If you send me an email at saabv4[at]saabv4[dot]com, we'll take it from there.
www.saabv4.com | |
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christophe
V4 Fanatic
France
227 Posts | Posted - 24 May 2022 : 13:00:17
| | OK, Melle. Will do it right now. | |
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Derek
V4 Guru
United Kingdom
2191 Posts | Posted - 24 May 2022 : 13:15:17
| | I didn't think that the transit engines were compatible with our Saabs so that is interesting. On "our" FoMoCo carbs the idle and main jet gets its feed from the same internal drilling so there might just be a bit of dirt there which is restricting the feed to the main jet. That would lead to a lean running condition at higher throttle openings. | |
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melle
V4 Guru
United Kingdom
3833 Posts | Posted - 24 May 2022 : 13:27:13
| Derek, we're talking about German/ Euro Transits here, which have the same Cologne V4 engine as Saabs. But it's definitely worth giving the carb a thorough clean as you suggest, diagrams/ explanation of how the carb works are in the workshop manual or the Haynes Carburettor manual.
Christophe, I'll get back to you tonight.
www.saabv4.com | |
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christophe
V4 Fanatic
France
227 Posts | Posted - 18 Aug 2022 : 11:31:14
| Hi folks,
Sorry for the late report, but this Forum has been down for quite a while.
Firstly, I want to say a big THANK YOU to Melle who fixed me graciously with the parts I needed and more, and all this for free!
Secondly, I want to report that my 1,7l engine runs much better with the 142 main jet. The bucking at constant speed has vanished and the engine responds very well. I have not checked the mileage yet but I will when the temperatures are down a little (let's say in December!).
Nice day to all. | |
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Derek
V4 Guru
United Kingdom
2191 Posts | Posted - 18 Aug 2022 : 13:08:02
| | Just as a point of interest. The very last 1.5 engines used a different main jet and float setting to the earlier ones. I think these carbs (different number) started at the time the Jubilee models came out. These numbers and settings aren't included in the Haynes. They are in the very last Saab engine supplements for the works workshop manual. If you have these Melle you can check. My complete and up to date WS manual went with the car when I sold it. If the 1.7 was used up to the final models there may have been jet changes with those too. | |
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christophe
V4 Fanatic
France
227 Posts | Posted - 18 Aug 2022 : 14:39:04
| | The successive setups are very well described in the 1967-1979 shop manual put online by Melle. Yes, they changed the Motorcraft carb in 1976 by using a manual choke, different idling and main systems and different (leaner) settings. During 1977, they switched a last time by using a Solex compound carb, that my car should have as a 1978 model , had it not been modified with a 1,7l Transit engine. | |
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| | Topic | |
Fomoco carb main jet. Anyone got a spare?
