128 coupe hard starting when very hot

Some confusion here. My car is a stock 74 SL Coupe, US model. It only had an electric pump, mounted where my picture shows. Now that is not the OEM Fiat pump. but it is mounted about where the stock pump normally goes. It is wired as Fiat designed. It is wired to two relays that control it by using the oil pressure sensor. Two relays as the pump must be running when the starter is cranking, as soon as oil pressure comes up the main relay powers the pump. No inertial switch. In most accidents the engine would not be running after impact. It is not perfect, but that is how Fiat did it. I would not over think this part as first, you need to fix the hot starting problem. Once you get there, then, if you need an electric pump, then we can help you design the wiring.
Yes some pumps are pass through, so you can run an electric pump in line with a momentary switch. The old Facet clicker pump did allow this, I think. When and if you get an electric pump you should be able to blow through the pump. I'd say suck on the output, but I don't want you to ingest any dangerous chemicals. So let us know what happens next.
 
yes, dont worry!! will not suck petrol, i swear it! and yes now i remember that you alredy told me about the safety system in your coupe, it involve cracking the engine to give consense to the pump, the motor must build up some oil pressure (but overcranking with the starter waiting for the oil pressure is what we dont like..correct?) probably back in the days technology was not enough for the modern inertial switch.

i will try wiring a cheap pump ( there is a china cheap version of the facet, around 15 USD).. must only decide to pull apart the tank (i want also get new plastic hoses because the old one are kinda stiff)
 
i was under the car this evening to scrap some body\surface rust in that zone (is the only area of the undercarriage that show some rust, but i should remove the leaf spring\suspension parts to get the chance of carry out a good job)..well no that room for a pump, there is that brake valve (i dont know exactly what is supposed to be..there is an arm that goes from the valve to the wheel hub)..on the other side there is the exhaust..what do you think about fit the pump in the trunk?
 
Just fit a new mechanical fuel pump and be done with it... chances are the pump is old and hot weather is precisely when they start to give symptoms of failing. Get a quality unit, there are sealed assemblies which also don't have an exposed pivot pin (a definite source of oil leaks) go for original Fiat or Fispa or Savara pumps... stay away from the cheapies they will cause you more grief.

SteveC
 
i Steve, yes i alredy ordered a savara pump yesterday..it was cheap so nothing wrong with trying first.. is it hot in bangkok these days? always a superloud city? i remember that any veichle in the city was drove at full throttle with apparently no exhaust silencer (even that red old liner buses)
 
Good advice from SteveC. That thing you saw under the car is an anti dive brake bias adjuster. I think it's function is to reduce front brake pressure when the rear suspension rises up. This is to keep the car level under braking. It's effect is adjustable. I'm not sure it does much, especially if the suspension is altered from stock. I replaced mine years ago as it was leaking. Good luck.
 
Other way around, as the front dives and the rear raises up transferring wieght to the front, it limits rear brake pressure to minimize the likelihood of the rear brakes locking which is never a good experience.
 
Makes sense to me, but I remember trying different adjustments and it didn't seem to make much difference. My car doesn't dive much so I figured it wasn't a big deal. Seems I heard that the "racer" boys, just took it out of the system. Of course that's probably with a lot of other changes. Now my old beta coupe would swap ends in a heart beat in the snow because the rears were locking up early. Never did fix that as it dissolved into rusty bits to the point I pulled it off the road.
 
i fitted a new SAVARA fuel pump.. well probably the car starts a little better.. say very little improvement.. problem is that when i restart hot, sometimes (not ever, but very often) the starter motor runs slow (the same behaviour of a flat battery, but battery is just fine) looks like the starter motor must fight against a big load.. (note that this do not happens with the motor cold)..once started the car runs just fine.
must look inside starter\relais\hig amp leads?
 
I would look at cleaning up the wiring to the starter motor, improve the ground connections from the engine to the body, the ground connection from the body to the battery and only after all if that look at rebuilding the starter motor. New brushes general cleaning etc.

If you still have the problem consider a gear reduction starter assuming they are easily available over there.
 
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If the starter turns slowly when it's hot then it's time to rebuild it... there will be wear and excessive movement at the bushes/bearing allowing the commutator to have too much clearance....and the area where the brushes run and the brushes themselves are probably very worn as well.

SteveC
 
well the starter motor was very tired: i sourced a refurbished one on UK ebay for 20 pounds and fitted it: night and day difference, so now with new fuel pump\good starter motor it's solved for the 99%, the 1% it's the long cranking needed when the car is unused for many days (carb priming)..but it's also a reason to drive it often as possible
 
This is why so many of us have switched to electric fuel pumps, so that cars driven infrequently can have the carbs primed with the electric pump rather than grinding away on the starter to get the mechanical pump to prime the carb.

In any event, glad you seemed to have the car running OK now.
 
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