87tbi starting problems - The 1947 - Present Chevrolet & GMC Truck Message Board Network

mfencl · 07-08-2012, 04:14 PM

I got a 87 v20 chevy 350 tbi, I'm not getting fuel to spray out of the injectors but one which is dumping the fuel I've replaced the ecm,fuel pumpfilter and relay, injectors,injector wires new distrubtor only thing havnt replaced is coil tps maps sensor and the thing next to maps sensor any ideas on why it isn't wanting to put fuel out need help
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gchemist · 07-08-2012, 05:19 PM

How old is the fuel pump? I've seen plenty of TBI trucks not start due to low fuel pressure. GM did not install a test port. You have to add an adaptor for a gauge or test at the fuel filter.

mfencl · 07-08-2012, 06:31 PM

honestly idk I'm guessing its orginal pump but not sure but wouldn't at least both get a little fuel coming out of em?
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gchemist · 07-09-2012, 07:54 AM

Nope. Fuel pressure is already low at 13-15 PSI for TBI. Pour a little fuel down the throttle body. Crank it. If it runs a few seconds, you have fuel delivery problem and electrical is fine. If it runs a few seconds, I bet the fuel pump is toast. I've being seen a lot of TBI fuel pumps failing latetly. Mostly due to age and heat in Texas.

rs72z · 07-09-2012, 09:33 AM

I thought you had already checked the pump? The rubber hose that connects the pump to the sending unit is probably bad if you here the pump running. If you drop the tank replace the pump regardless.

mfencl · 07-09-2012, 10:05 AM

yeah I'm gunna replace the pump this weekend and yeah that's what I've heard to that the pumps go bad and hoses too
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Don SC · 07-11-2012, 04:26 PM

Here's another possibility- the oil pressure sensing system . On the tbi systems, the fuel pump wiring is tied into the oil pressure system. If the oil pressure isn't sensed, power to the fuel pumps is interrupted by the ecm, and you get no fuel to the injectors.
Btw, if you turn on the ignition, can you hear the pump run? You should be able to, if there's B+ voltage to the pumps.

mfencl · 07-11-2012, 08:37 PM

yeah I can hear the pump I did a light test on a red wire goin to the pump n bulb was dim
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Don SC · 07-11-2012, 11:14 PM

The oil pressure switch is a backup for the fuel pump relay. It's supposed to prevent a no-start if the relay goes bad. But your relay is new, so I'm re-thinking what I said about the oil pressure system being a problem. It's probably ok. Since you can hear the pump run, the voltage is being sent by the ecm.
ftp://ftp.diy-efi.org/pub/gmecm/manuals/1227747/

07-08-2012, 04:14 PM	#1
mfencl Registered User Join Date: Mar 2012 Location: elpaso texas Posts: 24	87tbi starting problems I got a 87 v20 chevy 350 tbi, I'm not getting fuel to spray out of the injectors but one which is dumping the fuel I've replaced the ecm,fuel pumpfilter and relay, injectors,injector wires new distrubtor only thing havnt replaced is coil tps maps sensor and the thing next to maps sensor any ideas on why it isn't wanting to put fuel out need help Posted via Mobile Device

07-08-2012, 05:19 PM	#2
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	Re: 87tbi starting problems How old is the fuel pump? I've seen plenty of TBI trucks not start due to low fuel pressure. GM did not install a test port. You have to add an adaptor for a gauge or test at the fuel filter. __________________ Gerardo a.k.a. Mad Chemist Silverado XST videos

07-08-2012, 06:31 PM	#3
mfencl Registered User Join Date: Mar 2012 Location: elpaso texas Posts: 24	Re: 87tbi starting problems honestly idk I'm guessing its orginal pump but not sure but wouldn't at least both get a little fuel coming out of em? Posted via Mobile Device

07-09-2012, 07:54 AM	#4
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	Re: 87tbi starting problems Nope. Fuel pressure is already low at 13-15 PSI for TBI. Pour a little fuel down the throttle body. Crank it. If it runs a few seconds, you have fuel delivery problem and electrical is fine. If it runs a few seconds, I bet the fuel pump is toast. I've being seen a lot of TBI fuel pumps failing latetly. Mostly due to age and heat in Texas. __________________ Gerardo a.k.a. Mad Chemist Silverado XST videos

07-09-2012, 09:33 AM	#5
rs72z Registered User Join Date: Oct 2011 Location: Emory TX Posts: 900	Re: 87tbi starting problems I thought you had already checked the pump? The rubber hose that connects the pump to the sending unit is probably bad if you here the pump running. If you drop the tank replace the pump regardless. __________________ ___________________ 78 ccsb dually 5.3 4l60e http://67-72chevytrucks.com/vboard/s...d.php?t=491551

07-09-2012, 10:05 AM	#6
mfencl Registered User Join Date: Mar 2012 Location: elpaso texas Posts: 24	Re: 87tbi starting problems yeah I'm gunna replace the pump this weekend and yeah that's what I've heard to that the pumps go bad and hoses too Posted via Mobile Device

07-11-2012, 04:26 PM	#7
Don SC Registered User Join Date: Mar 2009 Location: Culleoka, Tenn Posts: 49	Re: 87tbi starting problems Here's another possibility- the oil pressure sensing system . On the tbi systems, the fuel pump wiring is tied into the oil pressure system. If the oil pressure isn't sensed, power to the fuel pumps is interrupted by the ecm, and you get no fuel to the injectors. Btw, if you turn on the ignition, can you hear the pump run? You should be able to, if there's B+ voltage to the pumps. Last edited by Don SC; 07-11-2012 at 04:39 PM.

07-11-2012, 08:37 PM	#8
mfencl Registered User Join Date: Mar 2012 Location: elpaso texas Posts: 24	Re: 87tbi starting problems yeah I can hear the pump I did a light test on a red wire goin to the pump n bulb was dim Posted via Mobile Device

07-11-2012, 11:14 PM	#9
Don SC Registered User Join Date: Mar 2009 Location: Culleoka, Tenn Posts: 49	Re: 87tbi starting problems The oil pressure switch is a backup for the fuel pump relay. It's supposed to prevent a no-start if the relay goes bad. But your relay is new, so I'm re-thinking what I said about the oil pressure system being a problem. It's probably ok. Since you can hear the pump run, the voltage is being sent by the ecm. ftp://ftp.diy-efi.org/pub/gmecm/manuals/1227747/



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