Author Topic: I have a 87 R10 TBI 350 long crank time after sitting hours.  (Read 5732 times)

Offline lehman368

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Re: I have a 87 R10 TBI 350 long crank time after sitting hours.
« Reply #15 on: May 29, 2019, 03:04:29 PM »
First of all it just a guessing game if you don't have a fuel pressure gauge on this. If you can get a hold of a gauge you can isolate the fuel pressure drop of either the supply side or the return side. If you cant get a hold of a gauge and see no external leaks or drips from the injectors it could be the pump check valve. But if does it on either tank its not likely. I know you said the TBI unit was rebuilt but my best guess would be the fuel pressure diaphragm seat. They are a highly polished seat that mates to the casting in the throttle body to close off the fuel return to the tank. If it is not seating good from say a burr it could be bleeding off.
Thanks


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Offline Irish_Alley

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Re: I have a 87 R10 TBI 350 long crank time after sitting hours.
« Reply #16 on: May 29, 2019, 04:44:05 PM »
for grins hook a jumper wire from battery to the 3" red wire on the fuel pump relay. this will bypass the ecm and energize the fuel pump. see how it starts and compare that to the noise you suspect is the fuel pump. this will energize the the fuel pump even with the key on
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Offline lehman368

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Re: I have a 87 R10 TBI 350 long crank time after sitting hours.
« Reply #17 on: May 29, 2019, 06:10:08 PM »
for grins hook a jumper wire from battery to the 3" red wire on the fuel pump relay. this will bypass the ecm and energize the fuel pump. see how it starts and compare that to the noise you suspect is the fuel pump. this will energize the the fuel pump even with the key on
Go from the positive side of battery to the red jumper line


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Offline lehman368

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Re: I have a 87 R10 TBI 350 long crank time after sitting hours.
« Reply #18 on: June 03, 2019, 01:56:06 AM »
for grins hook a jumper wire from battery to the 3" red wire on the fuel pump relay. this will bypass the ecm and energize the fuel pump. see how it starts and compare that to the noise you suspect is the fuel pump. this will energize the the fuel pump even with the key on
Go from the positive side of battery to the red jumper line


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I replaced the fuel pump relay Saturday. At first I thought it worked but after it set over night it still had long crank again


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Offline JohnnyPopper

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Re: I have a 87 R10 TBI 350 long crank time after sitting hours.
« Reply #19 on: June 03, 2019, 10:47:55 PM »
I have to say that this is what if frustrating: no follow up and no results

Irish suggests bypassing power so you can listen to the pump to see if there is a difference. That is huge in analyzing what is going on!

Since you have changed the pump we will never know unless you try again.

Have you looked for tubing issues that may have blockage, creating a vacuum that the pump has to overcome?
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline lehman368

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Re: I have a 87 R10 TBI 350 long crank time after sitting hours.
« Reply #20 on: June 04, 2019, 10:57:38 PM »
I have to say that this is what if frustrating: no follow up and no results

Irish suggests bypassing power so you can listen to the pump to see if there is a difference. That is huge in analyzing what is going on!

Since you have changed the pump we will never know unless you try again.

Have you looked for tubing issues that may have blockage, creating a vacuum that the pump has to overcome?
He I have responded I trying to find locate a fuel pressure gage. And I have replaced the fuel pump relay. I’m currently working 16 hours a day at my full time jobs and I have tried taking it to a garage to have them look at the issues they charge me $ 125- 200 and they tell me they can’t find anything. And I have same issues. I guess I have diagnose the problems my self and with the help of all of you Gus on here. Sorry  I’m only lucky to have 4 hours a week to try to fix the issues. I want to drive it daily but hope it will start and I’m not doing more harm to it. I would love to have 10- 20 hours a week to just work the bugs out of it and to get it preforming the way it should and be able to take someone a ride. So they won’t say why is it dose it do that. but that won’t happen until the middle of July with my work schedule right now. I have looked at the fuel lines from tank to fire wall from what I can tell they look ok not soft not cracked. Looked at fuel lines going to Tbi when it was rebuilt. When I bought the truck i have a Friend that was a dam good mechanic 70’a 80’s 90’ vehicles. Then  a little over year ago he was killed in car accident and I don’t have his knowledge and experience We put the engine and transmission back in the truck and had truck running great for over a year. It has always had that longer start issue he never got the chance to figure it out. And it truck also has a very slight bobble or could be miss at 35 mph to 50 when going the same speed in those ranges or letting up on the gas. It could  seem as a Slight out of balance tire. But it is not I have two sets of tires and dose it on both set. I know it’s not tires. I just put 500 highway miles on it last weekend no other issues than the two. I do have GM service books now and going through them also. But have not come across anything yet to help.with the issues. Thanks for all of your time and help. Tom


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Offline MIKE S

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Re: I have a 87 R10 TBI 350 long crank time after sitting hours.
« Reply #21 on: June 05, 2019, 05:12:19 PM »
Here is something to check that i forgot about. The relay is activated by the ECM. If the relay fails then the oil pressure switch next to the distributor will bypass the relay and activate the fuel pump. If it takes a few seconds to build oil pressure then that will lead to the fuel pump not coming on which would be long crank time. Now I know you said you changed the relay but that is only part of the circuit. ECM may not be activating relay. You have a power side and a control side of the relay. Look on this site in the emission book. It has the schematic of the fuel pump and relay. Study it to gain the knowledge of how the system works.   

Offline JohnnyPopper

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Re: I have a 87 R10 TBI 350 long crank time after sitting hours.
« Reply #22 on: June 05, 2019, 06:04:59 PM »
Sorry if I came across as a butt head, my observation is across the board, not just your issues.

On the tire issue, have you looked for a bent rim? Easy to miss.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline lehman368

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Re: I have a 87 R10 TBI 350 long crank time after sitting hours.
« Reply #23 on: June 06, 2019, 06:07:33 AM »
Sorry if I came across as a butt head, my observation is across the board, not just your issues.

On the tire issue, have you looked for a bent rim? Easy to miss.
No big deal just my frustrations also about this truck is a very nice truck and trying to make it run probably. I want to do other cosmetic things to the truck but I want it to run right first. But I will keep digging on it I will look at the oil pressure switch also and the way it works


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Offline Irish_Alley

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Re: I have a 87 R10 TBI 350 long crank time after sitting hours.
« Reply #24 on: June 06, 2019, 02:42:36 PM »
this is the schematic for the dual tank tbi


If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes