TheSamba.com :: View topic - Advice Needed

Wed Oct 01, 2008 3:54 am

Hello All

Further to my previous post of what my mechanic is telling me the other day, here's an update.

I've got a 1981 2.1 FI Westy (Californian Spec). It had a rebuild on the engine last year due to valve blowing and wrecking a cylinder. It's done 400 miles since then and has developed a serious fault.

The chaps at the garage are now sure the engine is ok - but it is still running terribly. No power, lots of backfiring.

They are sure it's a problem with my fuel injection system but they can't trace the issue. A guy (who I've known for 25 years) yesterday told me that he was sure replacing the FI with twin carbs (webbers) was a good option and that it would fix the problem.

Obviously, a running FI would provide better effeciency but I think Carbs are easier to fix etc...

After I had the engine rebuilt, the van was running really nice but it still only did 20 MPG at maximum which does make me think the FI has been on the way out for awhile? The other thing is that there is no Lambda sensor currently fitted for this van. The PO removed the cat and replaced the exhaust with a european style.

What does everyone think - fit the sensor see what happens? Keep trying to diagnose the FI problem? To hell with it and get twin carbs?

Any advice will be grately appreciated!

Wed Oct 01, 2008 4:18 am

You will probably get no one here telling you to replace the FI with carbs.
Carbs are the last resort for people who don't(or won't) understand a 25 year old Fuel injection system,
You had it running before with the fuel injection, so you have a bad part somewhere, and they want to take the whole system off for a bad part?
Carbs make it easier for the mechanic, not you the owner, you're the one getting hosed if you pay them to put carbs on there.

Wed Oct 01, 2008 5:20 am

mightyart wrote: You will probably get no one here telling you to replace the FI with carbs.
Carbs are the last resort for people who don't(or won't) understand a 25 year old Fuel injection system,
You had it running before with the fuel injection, so you have a bad part somewhere, and they want to take the whole system off for a bad part?
Carbs make it easier for the mechanic, not you the owner, you're the one getting hosed if you pay them to put carbs on there.

And carbs are older technology still.....

Not a good idea at all to go "backwards" to a carb. Just about every person I know that has done this conversion lost fuel economy and performance. Flat spots in the accelleration curve is common when an FI system is converted back to a carb. Maybe the carbs can be made to work, but there's no concrete proof that the FI is at fault yet. What diagnostics have been done to lead the tech towards the FI as being at fault?

No bad intentions to your buddy of 25 years (they are hard to come by these days), but he's from the old school. You'd be hard pressed to find anyone with FI knowledge recommending a step backwards to carbs. Unless you have a pristen relic you want to restore to originality, stay away from a carb if FI is already there.

Has anyone done the "basics" of testing the Fuel Injection system? Checked the fuel pressure? Checked the injectors for decent spray pattern? All simple enough proceedures. If the FI system checks out, then borrow a "brain box" and see what happens.

Backfiring under load sounds like an ignition problem. Hall Sensor checked? Wiring at the distributor checked? Coil checked?

You could change the FI system out with carbs, only to find out that the fuel system was not at fault. As our good diagnostic tech TENCENTLIFE has preached here so many times, identify the fault first. Ignition, fuel delivery, and compression. The 3 basics to an internal combustion engine.

Wed Oct 01, 2008 6:37 am

I would start by making sure that the igntion system, notably the distributor, is working correctly both advancing and retarding correctly and that you have no vacuum leaks.

I don't know if you have a vacuum line shared by the distributor running to the air cleaner (EEC valve) or not but the EEC in the air cleaner should be able to hold a vacuum. Test it with a hand vacuum pump or put a golf T in that line and see if that make it better.