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Username Post: 454 fuel pump rod and cam lobe problem...help        (Topic#201721)
454rollback 
Lurker
Posts: 7

Reg: 10-24-08
10-24-08 06:26 PM - Post#1549295    

I have a 1988 Chevy R30 2 wheel drive rollback truck with a 454, 4 barrel carb and mechanical fuel pump. Last week the truck stalled at an idle, started right back up an shut off again immediately, then would not start,,,,no fuel at the carb or out of the pump. I thought fuel pump was bad,,purchased a new one and installed another while having a hard time getting the shaft to stay up and out of the way of the fuel pump arm. Tried to start with new pump, and no fuel at the pump or at the carb. Again installed another new pump and this time the rod would not move downwards towards the small inspection hole plug or towards the pump... installed the new mechanical pump and still nothing at all. Yes plenty of fuel in the tank. I installed a new electric fuel pump and the truck started right up and sounded normal. I memtioned the chain of events to a seasoned mechanic friend of mine and he said that it was possible that the camshaft retaining bolt or bolts may have backed their way out and caused the cam to walk and the lobe is not lined up with the fuel pump rod, thus not activating the mechanical fuel pump any longer. I am concerned about this possible problem and do not want to be loaded up with a vehicle and have something go wrong and have to have my rollback towed by another tow truck...not cool...so i would appreciate any help or solutions to this matter. I do not want to take the entire front of the big block apart and find nothing wrong. I have not changed the oil since this fuel pump issue came up, and do not know if any metal shavings or debris is in the pan. Thank you for taking the time to read this post. Help !

 
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454rollback 
Lurker
Posts: 7

Reg: 10-24-08
10-24-08 06:28 PM - Post#1549299    
    In response to 454rollback

Forgot to mention that the truck has just 107,000 miles on it.

 
CDAUSA 
Needs to Get Out More Member
Posts: 12906

Loc: Texas Panhandle
Reg: 12-31-01
10-24-08 06:56 PM - Post#1549320    
    In response to 454rollback

Howdy,

I don't see that happening, going to the rear, the cam plug all but touches the cam, going to the front, well, all kinds of things aren't going to work. Cam gear will hit the cover, if the cam gear even turned slightly loose------it'd break the chain, it just wouldn't run long.

Best thing I can suggest offhand, is rig up a bumper, or disconnect the coil wire and have someone spin it over, while you reach in and push up on the pump rod----to see if it's "following" the lobe.

I don't know if it's seized at the moment, but regarding the mechanical pump, compare the old to the new, there were more than one style of "arms" for all generations of the BBC.

Is the arm on the old pump, made out of several strips of laminated steel, riveted together. Or just a stamped piece, smooth?

Check for wear on the rod if you can get it out, but as many as I've seen, I've never seen a pump rod eat up, or it eat up the cam. UNLESS, it was a roller cam that someone put the stock rod against, then it's in trouble.

Without being where I could measure one, I'd have to say the cam would have to move at least .500-.600" for the rod to lose contact.

 
someotherguy 
Moderator
Posts: 25749
someotherguy
Age: 44
Loc: Texas
Reg: 08-01-03
10-24-08 07:01 PM - Post#1549326    
    In response to 454rollback

Howdy and welcome to Chevytalk, from another wrecker driver.

I'm surprised your '88 was carbed, can you tell if it was like that from the factory or did someone convert it after giving up on a fuel injection problem? I guess if it had a fuel pump eccentric on the cam then either someone swapped it in, or it had it originally. Beats me.

My little brother had the exact same problem on an '80 454 but obviously that one was carbed from the factory, being 7 years before EFI. When the eccentric began wearing, nobody could figure out what it was because it would run for a while then quit. Let it sit long enough and it'd run for a while again. He finally figured out it was the eccentric and just put an electric fuel pump on it until he rebuilt the engine later before installing it into a different truck.

Anyway I'm about 99.9% sure the drive for the fuel pump on a Chevy cam is an actual lobe, not anything separate that bolts to the cam. The face of the cam is where the timing chain gear bolts on, and that's it.

I'd think 107K miles would be early for the fuel pump lobe to be wiped out, but it wouldn't be the first one I heard of. Hopefully someone that knows better can chime in.

Richard
94 C2500LD / 97 Suburban LS1 / 06 300C SRT8
Check out my truck shop projects


 
454rollback 
Lurker
Posts: 7

Reg: 10-24-08
10-24-08 07:07 PM - Post#1549330    
    In response to CDAUSA

Hi.. and thanks for you reply. The motor is not seized and seems to run and sound just like it always did for the year or so i have owned the truck. I did match up the old pump with the new and the angle and length of the fuel pump arm seemed exactly the same. I am not sure if the arm had several layers of metal or one solid piece. I did remove the pump rod and it did not appear to have any wear to it at all. I had put a breaker bar on the damper pulley and rotated the engine while i held my finger on the fuel pump shaft and did not feel or see any movement at all. I had someone hold their finger on the shaft inside the block as i cranked the motor over with the key and after about 3 attempts he said he did feel a very slight movement in the rod,,,just does not make sense, thank you again for you help

 
454rollback 
Lurker
Posts: 7

Reg: 10-24-08
10-24-08 07:15 PM - Post#1549335    
    In response to someotherguy

Hi, and thank you from one wrecker driver to another I do not know if the 454 was fuel injected from the factory or not, but back in 1988 i had purchased a brand new rollback truck exactly the same as the one i have now, and had a 4 barrel carb from the factory, only that was a 350 small block and this has a big block. One weird thing is that when i pulled the passenger valve cover off stamped on the head was pass..and not truck Not sure what that is about?

 
CDAUSA 
Needs to Get Out More Member
Posts: 12906

Loc: Texas Panhandle
Reg: 12-31-01
10-24-08 07:25 PM - Post#1549341    
    In response to 454rollback

  • Quote:
The motor is not seized



I meant the rod seized.

There is a cavity below the cam-----well, better way to explain it is, the pump rod runs in a machined boss/bore, it's about (guessing here) 2.5" long, then there's a ledge kinda thing before the cam. Use a good magnet and reach up in there far enough to get to that cavity, see if you can pull any fine metal grindings out.

If one's gonna wear of the two, it will be the cam but I can't see the rod not showing some damage from it.

If there is metal in there, just drag out what you can, find one of those telescoping neodymium types, it will get all that is relatively available. Then get you a spare electric pump to carry with you, get back after it.

My only concern is, check the fuel pressure delivered by the pump you have, make sure it's internally regulated back to 6 or so pounds.

Does it have a QJ on it? Quadrajet?

 
454rollback 
Lurker
Posts: 7

Reg: 10-24-08
10-24-08 07:37 PM - Post#1549348    
    In response to CDAUSA

Hi again, and muchs thanks for you advice and help. The truck does have a rochester quadra jet 4 barrel carb. The first time i removed the what i thought was a bad fuel pump, the shaft was very loose and kept sliding down and would fall out of the inspection opening as i removed the small cap bolt. After changing the pump the rod would not fall or move on its own and appeared seized or stuck in its current position, and after i installed a new and different pump that also would not pump any fuel. I should mention that the original pump still had alot of pressure on the arm as i tried to push it back and forth, felt like the same tension as the new ones, and i do not believe the diaphram inside the pump went bad as i did not smell or see gas on the dip stick. So i guess the pump is still working, but something inside stopped working or broke. I am going to change the oil tomorrow and use a paper filter to catch any metal or debris from the oil.

 
CDAUSA 
Needs to Get Out More Member
Posts: 12906

Loc: Texas Panhandle
Reg: 12-31-01
10-24-08 07:47 PM - Post#1549355    
    In response to 454rollback

The spring pressure you feel when moving the arm is just that, spring pressure to mechanically keep the pump arm against the pump rod.

How they failed was the diaphram breaking/splitting, and they wouldn't always, in fact never on anything I've ever owned, leaked fuel into the engine.

If I were back home, I could tell you right quick what the pump stroke/lobe stroke is, but I'm not. I do think it would be 5/8" or so, top to bottom.

And, it took just some force to compress the arm against the rod, and get the bolts started. One of those subjective things, but quite a bit of force. If yours went back on easily, then just screwed the bolts in, either the rod or lobe is history.

To elaborate on what I said earlier, if you can get the rod out and clean the area, don't put the rod back, just the pump or get a block off plate.

 
454rollback 
Lurker
Posts: 7

Reg: 10-24-08
10-24-08 07:58 PM - Post#1549363    
    In response to CDAUSA

When i put the first new pump on it was very tight and the bolts were very difficult to line up, get started, and hold up the shaft and get the pump shaft downwards and under the shaft which kept falling down and in the way... the second time i put a new and different pump in the rod stayed up and the pump went right on with no tension and the bolt went on easy. The first time the two bolts were very hard to move and i had to alternate back and forth putting a turn on one and a turn on the other, as i did not want to crack the aluminum pump housing. I will try tomorrow to remove the shaft and use a thin magnetic device and clean out the area you mentioned and drain the oil and see what comes out. The electric fuel pump that i installed was a low pressure unit and made to use with a carb system. Should i get a fuel pressure gauge and check the pressure going to the carb anyway ? I will check tomorrow and see if you had a chance to reply. I am worn out and stressed out by this mess, got to get some rest... thank you once again.

 
CDAUSA 
Needs to Get Out More Member
Posts: 12906

Loc: Texas Panhandle
Reg: 12-31-01
10-24-08 08:36 PM - Post#1549383    
    In response to 454rollback

Nah, it'll be fine, I just wanted to make sure it was that type of pump before we started a fire or flooded the engine with fuel. About 8 pounds is all the QJ N&S will stand, unless modified.

I'm sure you just want it running and forget this other mess, but I think the first replacement pump caused the issues. I'd have to dig til I found the culprit but I understand if you just want it going.

But, one last thing, was the original pump an AC? And was the first replacement, an AC/Delco?

And if you answered, I didn't catch it. Was the original pump arm just a stamped steel piece, or a laminated arm?

 
454rollback 
Lurker
Posts: 7

Reg: 10-24-08
10-26-08 06:54 AM - Post#1550160    
    In response to CDAUSA

Hi,, the original fuel pump was an ac... the first new one i put on was an airtex or airtec..when that did not work, i put on a carter and that did not work either. The original was a single metal arm as was the replacements. I drove the truck on the road for the first time yesterday and ran like it always does and after about 1 mile i came to a stop sign, then attempted to give it some petal trottle and the petal was on the floor and no power, just idled. I figured now what...i checked and the linkage to the carb came of an no sign of the metal clip that holds the linkage onto the carb...just one of those things...Truck drove good for the rest of the 5 mile trip. I still have to get a device and remove any metal in the area that you mentioned and change the oil and see what is in there... thanks again for you help.

 
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