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87 fuel problem

Discussion in 'Chevy Trucks' started by garjus87, Aug 1, 2003.

  1. garjus87

    garjus87 Junior Member
    Messages: 4

    I have an 87 chevy half ton 4 wheel drive. It has 5.7 fuel injection. The problem I have is after sitting for long periods of time (overnite) it cranks forever before firing. Its not getting gas right away. I have replaced the fuel filter. fuel pressure regulator,plugs,cap rotor,wires,coil. The fuel tank has been replaced by previous owner. any help would be great!
     
  2. wyldman

    wyldman Member
    Messages: 3,265

    Welcome to Plowsite. :waving: Seems we got a lot of new guys in here lately.

    Sounds like you have a bad fuel pump relay.The relay should come on when you first turn the key on for a few seconds to build fuel pressure.You should hear a humming noise from the tank,and a click from the relay on the firewall.It's a large black Bosch relay.

    GM's use backup power supplied through an oil pressure switch in case the relay fails.That's why it takes so long to start.It has to crank for a while to build enough oil pressure to close the switch,and then a few moreseconds for the fuel pump to build pressure.Then the engine starts.

    I don't have wiring diagrams handy,but I'll be back in the shop on Tues morning if you need any more info.I'd just pick up a relay and pop it in.It should fire right up :D
     
  3. garjus87

    garjus87 Junior Member
    Messages: 4

    I asked about the fuel pump relay prior to posting here and was told I dont have one by the parts store. I see one black thing on the firewall to the left of the dis. cap with wiring covered with black plastic tubing. Is this It? Will it click even if bad? do all 87 T.B.I fuel systems have the relay? I am desperate for help as this is driving me crazy! thanks
     
  4. wyldman

    wyldman Member
    Messages: 3,265

    Yes,they all have a relay.I do believe it is on the firewall beside the distributor.In 88 they moved them over to the pass side firewall.If you still can't find it,i'll check for you on tuesday,as I know I have a GM TBI manual with parts locations back at the shop.

    It may or may not click if it is bad.If the primary side of the relay is bad,then you won't hear it click.If the secondary side is bad,it will click.

    Hunt around under the hood,as you may find another relay you could swap it with to test it.You could also try a relay out of another GM product,as a lot of them are all the same relay.

    Don't get the relay from a parts store,goto a GM dealer.The aftermarket relays are more trouble than they are worth.
     
  5. garjus87

    garjus87 Junior Member
    Messages: 4

    I replaced the relay from the g.m. dealership. I was told this relay performs two functions, fuel and transmission. It seemed to start faster. I do hear the click now. I'll wait until tonite so it can sit for a while and see if there is improvement. Thanks again.
     
  6. wyldman

    wyldman Member
    Messages: 3,265

    Glad to hear you got it replaced....now hopefully that fixes your problem.Keep us updated.
     
  7. garjus87

    garjus87 Junior Member
    Messages: 4

    It does start faster now. I think you solved the problem for me. No more wear and tear on my starter and battery and other various ignition parts. One more question. I think the oil pressure switch is bad as my oil pressure will fluctuate between 0 and 60 at various times. Where is this switch? My oil is full so I know that oil is circulating. And its not overheating or anything like that. I just dont really know where this is located. thanks plow on!:)
     
  8. wyldman

    wyldman Member
    Messages: 3,265

    It will either be down by the oil filter,or just beside the distributor.It is usually covered by a little metal shield.

    They do tend to go bad,and the oil pressure gauge will fluctuate or read incorrectly.
     
  9. Mike 97 SS

    Mike 97 SS Banned
    from U.S.A.
    Messages: 1,106

    Yea, mine went bad once on my Chevy too a long time ago. The gauge was acting crazy, fluctuating all over the place. I cant remember exactly where it was located, but it wasnt hard at all to replace. When you go to buy a new one, they are going to ask you if you have a light or a gauge on the dashboard, mine is a gauge. If you cant find the old one on the motor, when you buy the new one, take it out of the box and get an idea of what it looks like so you know what your looking for. It will have only one plug-on wire going to it also. Good luck. Mike