If it ain't broke...? Vacuum advance, fuel pressure regulator

[KevAndAndi]

In many cases, I'm a believer in "If it ain't broke, don't fix it." There are a few things I've fixed that were broken (fuel pump, AFM, radiator fan thermoswitch), but also a few that weren't (radiator, coolant temperature sensor, starter). Those in the latter category were replaced because, as critical elements that were original to the car, and after 35 years and 117k miles, it seemed like it was prudent to do so.

Now I've got my eye on two more items: the vacuum advance and the fuel pressure regulator. They both appear to be original to the car. The vacuum advance is fairly inexpensive, while the FPR is more costly.

The VA contains a rubber diaphragm, does it not? Therefore, wouldn't this be covered under the admonishments to "replace every bit of rubber on the car"?

What about the FPR? What are its innards? Should it be replaced based on my car's mileage and age?

In general, I lean toward peace of mind rather than saving a few bucks and ending up stranded somewhere.

To be clear, there is no indication that either is malfunctioning, but neither has been tested.

[rridge]

Here's the problem with replacing original parts due to age only. Let's take the vacuum advance as an example. There are at least three different vacuum advance modules used on the Marelli electronic distributor. Two for carbed models, one for 49 state and one for California. FI models use a third module. Fiat Ricambi part numbers 9935889, 9936186, and 9936568 respectively.

The new Marelli sourced FI module were no longer available fifteen years ago. Exhaust heat kills them, and FI Spider were much more likely to be daily drivers. The carb modules remained available as new old stock (NOS) because they were one year only parts with little replacement demand. Some were sold to FI customers. Unfortunately they caused drivability issues on FI cars. Vacuum advance units from Eastern Europe appeared. Some worked on FI cars and held up in service. Some did not.

The fuel pressure regulator was made by Bosch and is still available from them. The part number is 0 280 160 214.

The problem with replacing original parts for age alone is that parts of the same fit, quality and performance may no longer be available. Buy from people you trust. Install new parts immediately. Verify performance. Hold onto the old part until you are satisfied with the durability of the new.

Richard

[spider2081]

Richard

Thanks Richard, I didn't know any of this.

I have replaced the vacuum advance on 3 FI Spiders in the last few years. All seem to function well. I purchased them from "Fun Imports Auto & Toys" in CT. The original ones had cracked diaphragms causing vacuum leaks. I really don't know if they are the correct ones for the cars but the cars run better than they did with the vacuum leak and no vacuum advance. I hadn't put the exhaust heat source and the diaphragm failures together but it certainly makes sense.
I have tested the fuel pressure regulators on the cars with a fuel pressure gauge. I "T" the gauge in the cold start valve line and they seemed good so I left them alone. I did check the vacuum line to the regulator to be sure it and the vacuum canister were on the correct throttle body ports. The openings on the ports are different sizes. but the hoses are the same size.

[KevAndAndi]

The problem with replacing original parts for age alone is that parts of the same fit, quality and performance may no longer be available. Buy from people you trust. Install new parts immediately. Verify performance. Hold onto the old part until you are satisfied with the durability of the new.

Richard

Thanks, Richard. Very informative. As far as keeping old parts is concerned, I literally keep every nut and bolt I take off the car! There have been very few exceptions. I have thrown away old hoses. Also, I think I tossed the old brake fluid reservoir because it was literally crumbling. That was a case of the new part being just as bad as the old, because the replacement Yugoslavia-sourced reservoir spontaneously cracked shortly after installation.

I think I will test the fuel pressure regulator. Seems like that's more of a "if it ain't broke..." situation. If I get a good pressure reading, it would give peace of mind. Regarding the vacuum advance, that seems almost certain to be bad, based in its age. I have been chasing vacuum leaks, and this may be a source. Can the diaphragm be inspected? Does the VA have to be disassembled to do so? Can the VA be removed without messing up the timing?

[rridge]

Here's the factory specs on the FI vacuum advance module. The vacuum is expressed in inches of mercury rather than psi: No advance until 4 in. of vacuum. Full advance at 14 in. A straight line steady increase between those points. Full vacuum advance is 15 degrees plus or minus 2. Not exactly a precision instrument. You need a dial back timing light and a pressure gauge that reads in inches to check.

For many cars, the bigger question is whether the centrifugal advance is still working and if so which of the many factory curves it is following. I don't see any info on the advance curves in the factory manual. I think I have found the FI info in the Fiat NA service letters circa 1982. Copies of all service letters are in the Mirafiori library but you must sign on as a forum member to access them. They are also up on Bradley Artigue's page.

And yes, the biggest question for old Spider owners is whether the vacuum lines are even connected and if so to the correct ports.