Alfa Romeo Forums banner

1 - 20 of 20 Posts

·
Registered
Joined
·
58 Posts
Discussion Starter #1
I have an 81 Spider. It runs like a champ for the most part. I live in Florida and when the temperature heats up outdoors, the low fuel pressure light comes on. The only thing that makes sense to me, is when the roads heat up, the heat radiating from the road is effecting the fuel pump. I thought I would run it by the experts before going out and spending $200 on a new pump. Thoughts?
 

·
Registered
Joined
·
9,977 Posts
Change the rear fuel filter and check it for clogging. Check the front filter as well. Also, check the in-tank fuel boost pump to ensure you're getting a good 3 psi out of it. Deadhead checking that pump is ok, but NOT for the main supply pump. Check the small connector hose between the outlet flange and the boost pump itself. They can crack, spray fuel inside the tank, and lower the outlet pressure and capacity.

If all this looks good, then it's possible that your main supply pump is weakening.

Go to Ingram Enterprises, Inc. || Spica Pump Rebuilds and download the free guides there.
 

·
Registered
Joined
·
58 Posts
Discussion Starter #3
I replaced the main pump and the rear filter. The problem is happening much less often. Though, if it is hot and I have driven for a half hour or so, the pressure drops and the car dies or SO close to being dead. The interesting thing is, is after I shut it off for a min or so, it is back to normal and runs great for the remaining hour of driving home.

It's very odd...about the only thing I can think of is to replace the pump in the tank, tho it seems like an unlikely candidiate.
 

·
Registered
Joined
·
9,977 Posts
Yes, a clogged vent system can do that exact same thing.

Did you download the fuel system guide from Wes Ingram's site? It's all in that.
 

·
Registered
Joined
·
58 Posts
Discussion Starter #6
Yesterday I had another issue, discussed in another thread, but it seems unrelated.

I had gone through the guide a while back and everything checked out fine. To eliminate the chance of it being vapor lock, I unscrewed the gas cap and started driving home. After about 40 miles, the low pressure light came on and it started lurching. It didn't die this time, it only lurched significantly. I pulled over, shut it off for a minute, then fired it up and continued my trip.

There are only so many things that would cause a low fuel pressure light, so this one has me scratching my head. :confused:
 

·
Registered
Joined
·
9,977 Posts
A slowly failing fuel pump can exhibit those symptoms as well. Eliminate all other possibilities first, however.
 

·
Registered
Joined
·
58 Posts
Discussion Starter #9
Since I have replaced the main pump and all 3 filters, I guess that I will have to replace the in-tank pump, unless there is some other reason why the low fuel pressure light would come on. Is there?
 

·
Registered
Joined
·
58 Posts
Discussion Starter #11
I confirmed that the little hose was intact and tight...

And the saga continues...

Yesterday, while driving home, the car acted up like it usually does on hot days. I pulled over, thinking I would let it sit for a minute or two. When I went to start it back up, it wouldn't. :( I narrowed it down to being my new Bosch main fuel pump...it had stopped working...and was only a couple of weeks old :(

Being stuck on the highway, and being resourceful, I bypassed the main pump and managed to drive it home under the power of just the in-tank pump...woo hoo. Luckily, I saved my old pump and put it back in.

I called IAP today to see what I needed to do about getting a warantee replacement pump. He said that I would have to ship it back and the Bosch rep would determine if the malfunction was caused by crap in the tank. I explained that I bought a new filter at the same time I bought the pump. He said there is no filter between the pump and the tank...freakin' news to me! Well, we'll see what their rep thinks...

I don't know about u all, but I have a filter....a VERY large filter between my tank and my pump. This is the filter I bought from IAP. He swears it is for between the pump and the engine...

Ugh...i love my car...i love my car :eek:
 

·
1966-2013
Joined
·
13,741 Posts
The big can filter is between the main pump and the fuel injector rail, not the tank and main pump.

Follow the the arrow path of 7 (feed from tank) to 9 (main pump) to 10 (filter)


However, there is a small sock filter that goes onto the in~tank pump to help prevent tank debris from getting into the system.
If its not been recently (or ever) replaced, its condition can be somewhat questionable to say the least.
pic:
 

·
Registered
Joined
·
58 Posts
Discussion Starter #13
I see...thanks for the info. Mine came with the filter after the tank and before the pump. That is where I installed it, since it seems more logical. After the pump and before the engine seems like the perverbial cart before the horse...
 

·
1966-2013
Joined
·
13,741 Posts
After the pump but before the rail ensures that the pump gets a constant and adiquate flow from the tank.
In~tank pump is really, really weak pressure~wise and does nothing more than pull up fuel to feed the main pump, as the main pump itself actually isn't strong enough on suction to pull fuel out of the tank alone. (even though the main pump is lower than the tank itself, once fuel level drops below 1/2 a tank or so of it can't even create enough siphone effect to pull enough to feed the engine)

Having the filter can before the main pump could viably reduce/restrict flow to the main pump enough that you'd have issues related to pressure and/or volume and would definitely create issues regarding the siphone effect if the in~tank pump were not completely up to snuff. The main pump simply could not pull fuel through the filter. (and in turn, if the in~tank pump were failing/failed, the main pump would have to try and pull fuel through that and the filter can. Not gonna happen even on a great day)

With the filter post main pump, it's getting juice shoved through it at up to 43~45psi, (with the potential to go upwards of 60psi if the regulator or return line is restricted), and as such the filter is designed to flow that kind of pressure, which in turn could also imply that it can't flow significantly less pressure (like the probable 2~5psi the in~tank pump represents) worth beans. It might pass fuel through, but at a severely reduced volume.

Our end user logic isn't relevant.
Allowing the mechansim to function as intended and designed is all that matters, because engineers and designers already used thier logic, and equally if not more importantly, calculations, formulas and tests to ensure the system would work as intended if assembled correctly using proper components.
EG: logically the hood should be hinged at the back rather than the front to allow easier maintenance on the belts, pump, dizzy, alternator, air filter, radiator and other sundries at the front of the engine as far more regular work is done there than at the firewall end of the engine bay, but it doesn't because mechanically and as designed the hinge and latch arrangement are part of the front crush zone and the effect would be lost if it were inverted. Another consideration is that the forward hinges prevent the hood from flopping up over the cabin and killing someone should the latch fail while travelling at speed.

Get the filter hooked up correctly before trying anything else.
 

·
Premium Member
Joined
·
1,473 Posts
The filter between the tank and main pump needs to be a Wix 33299 or equivalent due to the flow requirements of the Spica pump. The improper filter can lead to inadequate fuel flow which is necessary for injection pump cooling.
 

·
Premium Member
Joined
·
1,473 Posts
Okay.....**** DARREN'S EYES!!

Good enuff?
 

·
Premium Member
Joined
·
1,473 Posts
I'd hate to guess how many times I've said,"**** bifocals". Then I chuckle because I remember my Dad saying the same.
 
1 - 20 of 20 Posts
Top