TPITuned Port Injection discussion and questions. LB9 and L98 tech, porting, tuning, and bolt-on aftermarket products.
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OKay, I searched lol...so here goes...I have a stock 85 IROC 305 tpi and it is getting harder and harder to start when the engine is cold. When the engine has been running for a while, it starts quick It has to crank for over 12 seconds to start when it is cold b/f it will fire. I have surrendured to using starting fluid every time I start the car in the mornings. I have decided to fix the problem.....but what is it? I think it is the fuel pump. Whatda u guys think?
Part II if it is, what pump should I buy that I will not have to replace later down the road if I go with a carb 350? I was thinking perhaps an electric in line walbro pump? Thanks in advance,
stock TPI + in-line pumps arent very logical, but it can be done.
I wouldnt be so sure the fuel pump is causing your hard start,
the best way to confirm that is to test the PSI at the rail, and also
comb over your injectors with a voltohmeter carefully
Does the car prime itself?
'85 is a tricky year for me, not alot of knowledge.
The fuel pump should be audible after you turn your key to the ACC position.
It primes or loads your fuel to rail/injectors so the engine can start, then the
pump is constant when shes running.
Kinda hard to hear outside, you gotta friend with a spare ear?
yeah i have excellent ears and I can not hear it at all. My corvette C3 has an electric pump and I can hear it really loud. I understand the iroc is a mechnical fuel pump,.....and I think it is bad. So what is so hard about installing an electric pump? would a mechanical pump be okay down the road with a carb 350/350hp?...
Mechanical? weird, '85 TPI must be really crazy. Can anyone
with a '85 car chime in? That just doesnt compute with me.
An electric in-tank pump is the best thing, inlines just work
against physics.. They have to work really hard to draw fuel
out of a tank, and then deliver it with volume. For a EFI race car,
or carb setup, they are awesome.. not so much for stock EFI cars,
as they need volume and constant mild pressure.
Mechanical pumps are the best for a mild carb setup.
Im just trying to troubleshoot the pump you have, or in this case not have.
Ive not seen a mechanical that could run a EFI motor personally,
but im wrong alot too. I have zero experience with a '85 TPI system
at all.. I know they differ from all other tuned ports though. From what
Ive read you have a in-tank pump in there!
You could get a in-line to run the car until you mod it, people have
in-lines installed with their EFI so it works great no doubt.
Do what is necessary as I like to think!
I think my Arizona cohort has a '85 Trans AM, help!
I read this but still doesnt clue me in any!
Quote:
The OEM fuel pump for TPI/LT1 is an "in tank" fuel pump with an operating rating of 50 PSI and 24 GPH. This pump is recommended for all vehicles with in-tank pump mountings. We also offer a chassis mounted fuelpump which has an operating rating of 60 PSI and 30 GPH. This pump is also an AC DELCO unit.
Not sure if thats from GM or the service website offering the option.
thers no way you have a mechanical pump on a TPI. It woulnt run, a mechanical wouldnt produce enough pressure.
Also TPI cars with Electronic fuel pumps dont have regulators. a Regulator is for Electronic fuel pumps with carbed engines, taking all the pressure a electronic fuel pump makes (like 45-50 psi), and taking it to about 9 pounds. So its not the regulator, there isnt one. Also like The guy who has been trying to help you said, a TPI car wont start without a prime is right. Check your fuel pump relay, it may not be priming your car, but for it starting after a while is beond me. Good luck.
Last edited by Curtisyz54; 04-30-2009 at 11:43 PM.
I had the same problem. I had new injectors, a TPIS AFPR, and a new relay and it was still a female dog to start. It ran like crap, so I threw on a fuel filter and it was still bogging. Well, Sunday night, it would back fire and all the MAF codes came on. I checked fuel pressure and I'm sitting at 21 psi! Time for a new pump! I ordered the Racetronix from Hawks on Monday and still haven't gotten it yet but I'll let you know how it turns out. I'm surprised that it takes so long to get the pump but I will keep people informed of how it turns out.
I had an issue with a sticky/varnished up pump, it was very weak.
As well as a no prime problem once or twice. Cold start injector was
my third guess? Because the car did start, I have no idea why I assumed
it was a non-priming condition.
I had an issue with a sticky/varnished up pump, it was very weak.
As well as a no prime problem once or twice. Cold start injector was
my third guess? Because the car did start, I have no idea why I assumed
it was a non-priming condition.
lol, Imma rambler!
huh? No he said he car isnt Priming, But that is part of the Cold start injector.
thers no way you have a mechanical pump on a TPI. It woulnt run, a mechanical wouldnt produce enough pressure.
Also TPI cars with Electronic fuel pumps dont have regulators. a Regulator is for Electronic fuel pumps with carbed engines, taking all the pressure a electronic fuel pump makes (like 45-50 psi), and taking it to about 9 pounds. So its not the regulator, there isnt one. Also like The guy who has been trying to help you said, a TPI car wont start without a prime is right. Check your fuel pump relay, it may not be priming your car, but for it starting after a while is beond me. Good luck.
Actually they do have regulators. It is located under the plenum at the rear of the motor.
85 TPI is a little different but it's mostly in the ecm. When i first purchased my IROC I was told I would have to use starting fluid to get it going as it had a "Hard start issue". I never used it myself and the next day I replaced both the throttle position sensor and the idle air control and it has started fine ever since.
There is a small hose that connects the pump to the rail in the tank. Often it breaks and does not allow pressure to build. This will also make for a "Quiet prime". I would definately check your pressure at the rail(Passenger side of motor) and see what you get there.
Actually they do have regulators. It is located under the plenum at the rear of the motor.
85 TPI is a little different but it's mostly in the ecm. When i first purchased my IROC I was told I would have to use starting fluid to get it going as it had a "Hard start issue". I never used it myself and the next day I replaced both the throttle position sensor and the idle air control and it has started fine ever since.
There is a small hose that connects the pump to the rail in the tank. Often it breaks and does not allow pressure to build. This will also make for a "Quiet prime". I would definately check your pressure at the rail(Passenger side of motor) and see what you get there.
You should be able to rent the pressure tester from the parts store,
the fuel rail valve (looks like a bike tire valve) is at the back of the
fuel rail passenger side, under the plenum.
