[atlanta mistral]

In advance, thanks for the help to all. New owner of a 66 mistral. Likely the car had not been driven regularly. Still has the Lucas fuel injection unit. First day out of the garage, and as things warmed up, the fuel pump seemed to fluctuate. Found a problem with the leads on the starter switch, and cleaned. But fuel pump finally seemed to die. It did restart after cooling, but died again. Ignition switch hot to the touch. Finally pump would not activate when ignition was on.
Will try again in the am. Filter problem?? Pump likely died??
What sort of fuel pressure is expected?
Also might I ask typical idle RPM?
Best. Mark, Atlanta

 

[ivanthecarnut]

In advance, thanks for the help to all. New owner of a 66 mistral. Likely the car had not been driven regularly. Still has the Lucas fuel injection unit. First day out of the garage, and as things warmed up, the fuel pump seemed to fluctuate. Found a problem with the leads on the starter switch, and cleaned. But fuel pump finally seemed to die. It did restart after cooling, but died again. Ignition switch hot to the touch. Finally pump would not activate when ignition was on.
Will try again in the am. Filter problem?? Pump likely died??
What sort of fuel pressure is expected?
Also might I ask typical idle RPM?
Best. Mark, Atlanta

Hi Mark,

Welcome to Maserati ownership. I am also in the Atlanta area and own a 4.0 liter 1968 Mistral spyder. Fuel pumps can be a problem with the Lucas fuel injection system. I sometimes drive my car long distances and installed a second pump in case one decided to stop working. The factory did this on some of the early Mistrals. Some people have replaced the original Lucas pump with a modern Bosch.

Go to the page below on my website and download the workshop manuals for the Lucas injection system and pump. You can also download the owners and parts manual for your Mistral if you do not have them.

http://thecarnut.com/maseratimanuals.html

Send an e-mail to ivan@thecarnut.com and we can exchange contact information.

Ivan

 

[67alloy]

Hi Mark,
It's important not to let the fuel level run down low as it might seize the factory fuel pump. Even if not completely empty, it can start to draw up any sludge in the bottom of the fuel tank. You can hear the pump get a higher pitch to it as it cavitates.

Maybe what you thought was "cooling down" was actually the pump vacuum releasing and sludge from the pickup allowing a restart for a short time.

Not sure about the Mistral, but 3500s have a red light on the dash above the glove compartment which interrupts the fuel pump electrically if you do not have proper oil pressure. This may be faulty (it should rarely trigger in a healthy motor) and could be the problem as well.

The Lucas system requires a specific starting regime to maintain fidelity. Not sure if you have the fuel lubricated pump cylinder or the oil lubricated pump cylinder on your car. The former requires some careful attention to avoid mixing of fuel into your crankcase, thinning the oil and wearing the bearings.

Do you know which unit you have? Again, not sure if these were on Mistrals.

 

[atlanta mistral]

Thanks for the assistance. Car did indeed start this am, but ran only a few minutes. Cleaned the fuel filter and reservoir, and no real change. Found a power increase on the pump as it was run, and the pump became warm. Pump motor was disassembled, and found loose wire shards broken from the wrappings, some having scarred the housing. Cleaned and removed all wires, and reassembled. Then lowered the fuel return valve pressure by removing some of the shims. Car can now run at least 30 min at idle.
Ivan mentioned via email that I needed to have at least 100 lbs of fuel pressure. I did measure after all of this and found I now have 90 lbs. Am I at risk to do damage to either the Lucas FI or the engine?? Should I replace the shims to try to elevate the fuel pressure?
Indeed all of this seemed to start yesterday after pushing a yellow button on the dash---likely the relay mentioned. Should I still try to replace this? (Given shat was found in the fuel pump motor, more problems were close at hand.)
As for the type of FI lubrication, I am at a loss to know. Ivan sent his grand link, and I hope to be better informed soon. I will just add that there was no gas odor noted on the dip stick tonight.
Again my thanks. It has been a long few days, but I am still excited. Best. Mark

 

[ivanthecarnut]

Wet versus dry injection

Mistrals had both the wet and the dry injection system. Wet means that engine oil is used to lubricate the fuel distributor while dry means that fuel is used as a lubricant. Unfortunately the wet type has the nasty habit of sometimes diluting the engine oil with gasoline, especially if you leave the pump on when the engine is not running.

These two photos show a wet and a dry system. Look at the plug towards the rear of the fuel distributor. If it is stand tall, the system is wet, like on the red car. The silver car has a dry system.

Ivan

 

[ivanthecarnut]

Thanks for the assistance. Car did indeed start this am, but ran only a few minutes. Cleaned the fuel filter and reservoir, and no real change. Found a power increase on the pump as it was run, and the pump became warm. Pump motor was disassembled, and found loose wire shards broken from the wrappings, some having scarred the housing. Cleaned and removed all wires, and reassembled. Then lowered the fuel return valve pressure by removing some of the shims. Car can now run at least 30 min at idle.
Ivan mentioned via email that I needed to have at least 100 lbs of fuel pressure. I did measure after all of this and found I now have 90 lbs. Am I at risk to do damage to either the Lucas FI or the engine?? Should I replace the shims to try to elevate the fuel pressure?
Indeed all of this seemed to start yesterday after pushing a yellow button on the dash---likely the relay mentioned. Should I still try to replace this? (Given shat was found in the fuel pump motor, more problems were close at hand.)
As for the type of FI lubrication, I am at a loss to know. Ivan sent his grand link, and I hope to be better informed soon. I will just add that there was no gas odor noted on the dip stick tonight.
Again my thanks. It has been a long few days, but I am still excited. Best. Mark

The car will run with 90psi of pressure but it may miss under load. Have you tested how many amps the pump is drawing?

Current to the fuel pump goes through the ignition switch, amp meter, low oil pressure relay and who knows how many other connections. Any time there is a connection in an electrical circuit there is a good possibility of adding resistance, especially when these connections are now 35 years old. An easy, and very practical modification is to add a relay. You can take current directly from the starter and use the present connection to the fuel pump to trigger the relay. Make sure to include a fuse in the wire between the starter and the relay. The relay can be located next to the fuel pump and nobody will ever see it.

On the Mistral the pump is located on the front right fender, which is a long way from the gasoline tank. One thing I did on my car was to add a low pressure feeder pump near the gasoline tank. That way the Lucas pump did not have to work so hard to suck the fuel. A small electronic fuel pump that you can find at NAPA works nicely.

Ivan

 

[67alloy]

Good info, Ivan.

Let me ad, you really do need a good 100psi for the car to run properly. To that end I would replace the fuel pump with an aftermarket pump that can supply 100psi. You may need an inline regulator. The noise of the stock pump running takes away from the enjoyment of the car, IMHO. Part of that is the location, but a new pump will run quieter.Keep the old one in a box for purists who wish to return it to stock.

Clean up all the contacts (and grounds!) that Ivan has identified in the circuit. Hopefully it ends there and you dont get into the F.I. unit itself. That gets a bit messy.

The theory on the "dry" F.I. system is that the oil and fuel pressure must be balanced. An O ring separates the two in the F.I. distributor cylinder; if one pressure exceeds another it can distort the seal and you might get "peanut butter in your chocolate" and vice-versa. Hence the fuel shut down relay which deactivates the pump if it fails to sense proper oil pressure. This can occur in healthy engines after a long sit between start-ups, as the oil galleys have drained back to the pan and have a delay in priming.

Smelling your dipstick and noting exact levels are clues to whether you are leeching fuel into your oil.

 

[Derek23]

F1 pump replaced

Just fitted new pump. Fuse keeps blowing when I switch off engine and pump wont switch off. Any ideas guys? driving a 4200 coupe.

Just doing my head in

derek23